Hi and welcome to YT!
When i first got my yorkie at 13 weeks i had her in a crate with 3/4 of it blocked up so she only had enough room to go in, turn around, and lay down in. I didn't want to give her lots of room to sleep on one side and potty on the other. I too came home at lunch to let her out for the first few weeks. So for a few weeks i kept her in the small crated area. Then once i felt sure enough that she could hold it i unblocked more of the crate for a few days, and then some more, etc... until she eventually had the whole crate. She had the whole crate for a little while. Next step, I bought an ex-pen and she graduated to this when i knew she could hold it for longer periods of time. She did really well but then had a lapse and started pottying in there so back to the big crate again for a few days. I did put a potty pad in the ex-pen just in case but she chewed it up instead of pottying on it so that was the end of that. She stayed in her ex-pen when i was gone for a very long time, at least a year and a half, maybe more.
I didn't feed her in the crate either but she did have a water bottle (like a rabbit water bottle) attached to the crate so she had access to water while she was in there. Mine also didn't want to play in the crate but i did leave a safe toy in there anyway, plus a few blankets or a bed.
If you transition to bigger areas slowly you shouldn't have a problem. If she has a lapse in the potty training then simply go back a step to the last smaller area she did well in.
edit: link for ex-pens
http://www.jbpet.com/Dog-Exercise-Pens.html just so you can see what they look like