The base CL 4 Elite Trooper:
NH8/Soldier1/EliteTrooper1
STR 12, DEX 12, CON 12, INT 8, WIS 8, CHA 8, (+6 remaining, up to +4 in any one)
BAB: +8; Defenses: REF 18(16)*, FORT 17, WILL 11; hp 49
Feats: AP (light, medium), Martial Arts I, Point Blank Shot: +2 starting feats, +2 General Feats
Talents: 1 from Armor Specialist, Weapon Specialist, Commando, or Mercenary (FU), +1 from Elite Trooper
Trained Skills: Any one except UtF
Equipment: Combat Jumpsuit (+4 armor) because an ET is going to wear armor until heroic level dictates otherwise.
This build is using the non-heroic (average) stats equivalent to PB 15 and then includes a total of +3 in level boosts with no more that +2 in any stat. You can get a 16 with it but should stop there. Hit points are calculated using fixed hp/HD equal to 2/3 or 3/4 max (depending on how you round) hp for each level; this means I'm giving 3 hp/level in Nonheroic, 7 for Soldier, and 8 for ET plus the CON bonus of course. With only 2 heroic levels and all of these armor feats this character REALLY should be wearing armor; I included the basic Combat Jumpsuit here but really would expect 'trooper armor or medium battle armor in most cases.
This build also uses NH8 which is counted as CL2. Now NH6 is also counted as CL2 and stepping up to NH8 may give the biggest variation in power (BAB and hp/HD) you'll find in a single Challenge level equivalent. It may not be spelled out anywhere in the books but it takes 3 full levels of NH for a +1 CL (basically +1 CL for each additional feat it earns) so NH6 and NH8 are both CL2 despite one being a good bit stronger. A future post will talk about pulling back the levels in NH but we need the +6 BAB from NH8 to go with Soldier's +1 to reach +7 so it stays. If facing stronger (higher level) PCs this little bit extra at CL2 does help the NPC present itself as a challenge.
Now what you should notice is that this basic build still leaves 7 "slots" to fill although the Soldier talent is somewhat restricted. Starting with feats we're figuring that AP (light and medium) in the ET requirements are coming as starting feats from Non-heroic and possibly Soldier which leaves two starting feats, most likely for Non-heroic, which will likely provide the character with it's Weapon Proficiency and possibly Skill Training/Focus if it doesn't want/need the weapon proficiencies. As a 10th-level character this would start with four general feats but two of those go for the ET requirements leaving you with two general feats that could be spent on most anything. Unless feats/talents dictate specifics this build doesn't require any specific trained skill so the skill is left unassigned. With the talents you need the Soldier talent to meet the ET entry requirements but the ET talent can be any it qualifies for.
Now where to go with this base? Here are some examples:
Now Autofire Sweep is actually very sick depending on what template you use for it; I've got house rules in the works for it but sufficient to say it covers a MASSIVE area in which the first pair of this group suppresses with Improved Suppression Fire to give them all -2 on their attack even if they don't suffer any damage. This group is all utilizing Controlled Burst from ET to reduce the attack penalty from autofire which will help them deal damage. The damage dealer is trading the control aspect for the single shot potential of Burst Fire which can be very helpful if an attack needs to be aimed to avoid cover as the cover means the attack needs to hit REF anyway for any damage.
Still need to pick a weapon with this one or could pick another skill. May also drop to 'trooper armor for more mobility. In any event this is the kind of character you could put beside almost any other character and essentially give that character an additional 70 hitpoints. A load of hp for the CL and plenty of resistance to damage. Harm's Way requires planning but can make sure shots go toward this elite bodyguard instead of the charge; Bodyguard's Sacrifice is there to make sure he can take the damage even if he can't activate Harm's Way and also to cover the things that might get around Harm's Way for damage. For the extra feats Never Surrender will give this character a chance to soak a shot that would drop it to zero hitpoints; Stay Up is a way to make sure that shot dealt little enough that Endurance has a good chance of working with Never Surrender. Take Second Wind when you get the chance and remember that Delay Damage can keep you protecting your charge even after you should be dead.
Want to make the primitive tribesmen dangerous? Here's one wy. You can vary the weapon and also add more armor but charge in with +15 on the attack that's got chance against MUCH higher level hero and the damage shouldn't be ignored. Fleche makes the charge that much more dangerous as crits come more easily. The talents are little up in the air but Merc's Grit was taken to really stick any CT penalties this might get to the PCs. When it comes to the ET talent there were so many that dealt with criticals making them more dangerous but it's also a strong melee option.
Perhaps your most basic "Elite Trooper" as this guy really isn't out to do anything fancy but just layout hurt with a rifle. You could move feats/talents around depending on what you want but if you want someone who just shoots with a good bonus for high damage this works.
Probably not the first thing you think of when you think Elite Trooper. While the Bodyguard can soak/prevent damage this guy can heal damage very efficiently. He's got an open starting feat for a weapon if he carries one otherwise it might be another trained skill. With his surgical skills he can patch up a number of allies pretty quickly. Indomitable is taken so he can be sure he's a the top of his game when it's time to heal while Strength in Numbers helps him stay going despite nuisance fire.
Boom, boom! Haven't really worked a lot on what general feats work well but the talents help a bunch. Mandalorian Advance was taken to enable him to get close to a place he wants to place an explosive but wants to minimize his time there; the talent will let him move out there before using the Full Round action to place an explosive or disarm one if needed.
These stubs are just showing how this CL4 build can already have all the requirements lines up for entry into a couple OTHER PrCs. You may also notice that some of these do NOT overlap and you could me the requirements for Officer and one of the +4 REF Classes with the CL4 build.
Additions:
These are specific variations on the normal CL 4 Elite Trooper intended for use in vehicle operations. They do not specifically benefit from the standard reasons for wanting ET in your NPC build (that being Delay Damage & FORT) but rather point out some of the other reasons for taking the class. The Pilot version is ready to enter Ace Pilot and shows a high damage version using Burst Fire/Controlled Burst and then the high accuracy version utilizing Weapon Focus/Specialization/Greater Focus. The gunner version isn't as Ace Pilot ready (but could still serve as a good pilot or in another skill position) but instead looks at two ways to start boosting the vehicle damage potential; the burst fire option is the same as for the pilot except that it now benefits from Focus/Specialization (and if he were the pilot using the pilot controlled weapon it'd be +9) while the other is going with the multiple attack option which can be very strong on vehicles. Neither of these stat blocks includes the vehicle's fire control/INT modifier or other modifiers from the vehicle.
Addition/Edit: The vehicle versions may show a lower CON but for these examples I make the assumption that you want a character with more than a few hitpoints and thus the CON 12 assumption as a base line. If you want more of a glass cannon type character you could start dropping CON and use those points to boost some other ability scores. For each point lost in CON modifier you lost 10 hit points and -1 from the FORT/DT; at CON 8 you pick up 4 more points to spend in other abilities but drop to FORT 15 and hp 29. If one figures average damage taken at 15 points a hit at CON 12 I'd figure you could take four hits and just be standing yet but going to CON 8 you now go down after just two hits; if that's what you're going for you might even expect them to withdraw after getting hit once.