Perhaps they could give different functions to the engineer. A fixer could hack a tower and disable its alarm for a time. An engineer could hack a tower and disable the benefits it gives for a time? Or somesuch. It would be rather cool for engineers to be able to turn off that nice 'huge bonus hp' advantage for 10 minutes or so during a fight
Certainly raise the bar on 'who to gank first'. Now its a toss up: Nuke the doc! No Nuke the NT! No nuke the trader! Hehe