As far as I know, baseball players would not even consider practicing with a heavier bat; if anything it would do damage to their finely-tuned swings rather than help them swing faster. Remember that in baseball it isn't always about how fast you can swing the bat.

From personal experience, I could see how training with, say, rusty hubs and then racing with sweet ones would help, but again for the same reason that baseball players don't practice with heavier bats: it would mess up the feel of the bike. You get used to the bike accelerating a certain way, cornering, certain speeds feel a certain way, etc.

You mention that ball players warm up with donuts - this is true, for warming up and for that slightly faster feel, but like those tricks that everyone learns in second grade that make you feel like you're lifting something up or pushing outwards, the effect only lasts for a certain period of time. Training with a significantly heavier frame/bike might make you over-ride your race bike, going too hard because it feels faster.