I think the Shelter SPY should be re-introduced.

Back before 2.2, most spys would spec to use shelter, made possible by popping a nightspider.

Then came 2.2 and the re-balance flop, and now we're stuck with nanites for healing/resists, and I thnik it's fair to say that most players dislike this.
This also makes the 20 PSI levels of the spy almost irrelevant, a shame really, especially when considering how only missions gives PSI xp to spies.

In short, please get us rid of nanites.