I'm betting this has been suggested before, but I can't find it on the boards atm.
Currently there is only one nano which morphs Engineers into a bot: Slayer Transference.
An entire line of nanos should be added which morphs Engineers into each bot type. I.e. Automaton, Android, Gladiatorbot, Guardbot, Warbot, Warmachine, Wardroid. It would also be good to add other Slayer morphs. Each morph would buff certain skills, etc. One might buff Ranged Energy, another might buff Heavy Weapons, another might buff Grenade, etc. Each would come with their own AC buff, and each AC buff would be a different type. It might also be interesting to include a small reflect buff of a specific damage type as well.
The whole point of making each buff specialized is to force choices for different occasions. No one buff would be good all the time.
Making new nanos is obviously something that Funcom can do very easily, the only real effort is in figuring out what numbers balance best. As for the morphing thing, hopefully it would be a simple matter of copying Slayer Transference and changing the 3D modeltype.