Combat effectiveness is extremely closely tied to awareness on the battlefield, being the one to shoot first is the most decisive part of combat. So I strongly disagree with you regarding the mines and spitfire. If I get a clue as to where the enemy is coming from I can typically estimate their future location and ambush them. Just earlier today someone ducked out of sight from my spitfire and I caught them reloading with my shotgun where they went to ground. It was pretty darn effective if you ask me, I'd have never known I was being flanked otherwise. But since you do clarify that you want something that boosts your survivability I bring you back to the MANA turret and where I said that with the correct implants you were difficult to shift. Specifically, Jockey 4/5 and Robo Tech 5 grant you +50% shields and -25% damage received respectively while mounted to the MANA, Robo Tech 5 also heals any damage you do take and does so even while under fire. You can equip Hardlight Barrier instead of mines/C4 and MANA in its slot allowing you to set up in mere seconds, you'll have 750 Shield recharging 2 seconds faster than non-Engis and 500HP regening at 25 HP per second. The MANA shield and Hardlight barrier mean that short of precise fire you'll not even be taking damage and regarding precise fire a Sniper headshot leaves you alive in half health. Now would you care to explain why that is not combat effective enough for you? Whereas now it seems like an imitation of the Heavy's ability. Except harder to use because you have to lose all your shield first to get the most out of it. You're right, it's not game-breaking, it's just pointless. As I said the Heavy's overshield is preferable for what you describe or a medic with Carapace, there's no gap it's filling it's just creating a new quasi-class.