To run 2 separate coils on the same pump could be a bit challenging as far as keeping things balanced. You'd never be able to properly set subcooling (as a condenser) to optimum numbers as the condensers will almost certainly be of different capacity and size. You would almost be better off running the condensers in series. You could run 2 evaporators together in parallel, or selectively, if you had properly set up properly rated TXVs as they could compensate for the load change if one branch is shut down (single valving to avoid trapping unknown amounts of charge in one coil). Fixed orifice metering would be out of the picture as there would be no way to properly set the charge. You may be able to have selective condenser usage with txvs and a suitably sized receiver. Is this going to be a reversible heatpump or a straight heat/cool system? It could become quite complex requiring 4txv, multiple valving, and a nightmare trying to set superheat/subcooling, all while still achieving a suitable oil return to the compressor. The simplest approach would be to run your coils in series if possible, and have selective use of the fan on the air over coil (such as pressure/temperature).
To your question of piping, Oil return on long runs can usually be assisted by using traps and inclining the return line in favor of the compressor. The pipe size is directly related to both pumping capacity and length of run. Ill have a look around and see if I can find a suitable loss chart that can help select the correct size for your installation. There is a (small) efficiency hit due to frictional losses in the pipe, but unless its a very long run, you'll never see it.
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