This is really neat. Didn't realize Tameshi cared about bouncing to any hand (rather than just your own) until I read this, so that's pretty amazing. I'm not going the vehicle angle with this deck personally, but it's interesting. Some suggestions:
You're likely going to be behind on lands with this deck every turn, so you can consistently trigger the "oops I'm behind on lands better get some more" effects that white has. The cards I'm specifically thinking of are
Archaeomancer's Map and
Oath of Lieges, both of which give you free lands as long as you're behind on lands.
The card
Attunement basically reads "Draw 4, discard 4" if you have Tameshi out, which is nice bc any artifacts and enchantments you discard you can use later.
All the MDFC lands are excellent for this because you can play them as lands, then bounce them and cast them as sorceries later.
Sea Gate Restoration is expensive, but
Emeria's Call and
Ondu Inversion are both worth exploring in my opinion and are much more affordable.
It's an expensive recommendation, but if you happen to have an
Urza's Saga, it's unbelievably good here, as you can recur it with Tameshi. Also expensive, but
Crucible of Worlds gives even more options and lets you do things like
channel Otawara, play it from the graveyard, bounce it to hand, cast it again, etc.