It's just a matter of being creative with how you use those abilities. Those which are more blunt, more suited to 'combat' are often far less versatile. Jerome is barely better physically than anyone he'll go up against. Emilia has an unparalleled ability to manipulate others, especially in times of stress. Devan can actually pull off gun kata (YouTube Equilibrium). As for upgrades,I imagine Jerome could heal so fast as to be near invulnerable, Emilia could manipulate the emotions of an entire crowd (political ambitions? Riot?) And Donovan could develop remote sensing, or maybe even vision across other spectrums. The only limits are the ones you put in place for yourself.