I wonder if Deadpool's insanity would act as a natural defense against Xavier's telepathy, the way Rouge's "fragments from multiple minds" things works to keep them from messing with her memories? I'm sure Cyclops couldn't do much against him, but Wolverine or Jean could slow him down or "Phoenix" could destroy him.
(I was thinking of having "Phoenix" as a kind of sleeper agent the Professor caged inside Jean, with it as an ally or a slave, or maybe something of both. Maybe he has to use Cerebro to put it back in the cage, so he only lets it out for the most important missions.)