Keitai mail and (non-japanese) smart phones: will I lose anything by going with b-mobile over softbank?

I'm moving back to Japan for a year and I'm looking at ways to save money on my phone. Especially not keen on getting hit with a 10.000 cancellation fee when I leave.

My current phone is ZTE Blade, which is a rom installation away from being a Softbank 003Z. So, if I go with Softbank I'm fairly sure I could use their S! Mail just like a proper Japanese phone. (I also have my old Softbank dumbphone I can show them, so getting a SIM card without a new phone shouldn't be impossible).

If I instead choose to get a b-mobile SIM (for cheaper data and no cancellation fee), will I lose anything by not having a normal keitai mail address? My concern is mainly with communicating with my Japanese friends, who have normal Japanese phones and plans. Do those play nice with gmail these days? Or do b-mobile contracts come with an email that does?

Also, does anyone know how strict b-mobile is with their 1-year contracts? Will they even sell them to people one a 1-year visa? Or do they somehow force you to cancel when you leave the country (instead of letting the contract run its course, if that's cheaper)?

Bonus question: Has Softbank really stopped selling anything but 2-year contracts? Last time I had a contract, I was able to cancel after 6 months with no penalty...