The engineer abilities don't really help with the power consumption much. You'll most likely equip around what you can do full time, as opposed to only while a buff is up. So of the 2 engineer buffs that are power related, only one is really nice and that is primarily because of the +20some to power, not the EPS aspect.
The bigger downside will come from your inability to train your engineering officers. No EPtShields III, no Engineering Crew III. At least not until (or if) they make it so we can actually sell officers we've used...or train ones we haven't used and then put 'em up on the market. Not necessarily that big of a deal either, my cruiser in beta didn't bother with rank III of either of those powers.
So I wouldn't say you'd be gimped.
But, for what a cruiser is good at, the ability to soak lots of damage, engineering's abilities definitely serve to build upon that.