That idea STINKS ON ICE, is stupid, and yes, it IS illegal, to announce such things; especially at this stage of the primaries.
No, not illegal. You can think it’s stupid, but it is not illegal. Even with a patronage job, as long as you don’t name a name, you can hint. With a USSC position, however, you can go pretty far. Rutherford Hayes did this in the Compromise of 1877.