friction shifters are a pain in the a-- with 8 or more gears in back, way too fidgety. I wouldn't even think of trying to use them with a 9 or 10 speed system.

you can't use mountain derailleurs with road index shifters, either, at least not in 9 or 10 speed, maybe 7/8 speed is OK but noone MAKES index road shifters in 7/8 anymore.

the hand positions are all wrong for using mountain thumb shifters.

oh yeah, road brake levers are strictly short pull, so if this bike has V-brakes or mechanical disk brakes, you're hosed. at least v-brakes could be swapped for CX style cantilever brakes. with disks, ugh. and if you have hydraulic disks? double ugh. maybe you can put a CX disk brake system on there, I dunno.

really, I think you'd be better off buying a suitable road bike, maybe a CX, or maybe something like one of the Surly touring bikes.