Unfortunately, that would also destroy the LCD and quite possibly the crystal oscillator (not sure how strong the metal can enclosure of those things are). Battery wouldn't survive it either but you could easily take it out and insert it after the vacuuming.
I have no idea how tightly those things are sealed. Given some of the watch tests in this thread (the olive oil one), it surely can withstand the positive pressure but I'm not certain it could withstand negative pressure. If oil got in there, that oscillator would never keep the correct frequency again.
Unfortunately, that would also destroy the LCD and quite possibly the crystal oscillator (not sure how strong the metal can enclosure of those things are). Battery wouldn't survive it either but you could easily take it out and insert it after the vacuuming.