I'm rebuilding my commuter bike, and I intend to reuse components from a road bike to do so.
The mountain bike is a Specialized Hardrock sport from 2005. It now runs avid bb7 discs. These will stay. the cranks, fd, rd, and shifters will be replaced.
The donor shifters are shimano DA 7800. The new RD and FD are XTR 971 (complete overkill, but they're what I have to work with). The cranks are 50-34 compact. The cassette and chain are shimano 10 speed.
I already have the problem solvers to handle the difference in brake pull.
The reason I'm using the XTR FD is that it can be set as top pull. If I could use a bottom pull only FD on that frame, then I'd have any number of options. I'm aware of the problem solver pulley to convert a top pull cable to bottom pull. I think I'll just install the parts as planned, and look for another solution if I find I have a problem.
It's likely you'll have problems- dropped chains, bad shifts, can't get the front derailleur aligned properly. Although with only two rings, it won't be as bad as it could be. The road groups and the mountain groups pull a different amount of cable in the front. Best get the shiftmate...