I thought they use same seeding algo as electrum (or for this purpose any other deterministic wallet)
so if you're brave enough  you can start using trezor with a seed generated 'elsewhere' and your problem's solved
you'd have your keys anywhere where you'd restore the seed

adding some mathemagic, you could initiate your trezor with a seed derived from a master seed so that you do not even mix key/address pairs from trezor with the rest of your key/address space