In Grant Petersen's book Just Ride is a chapter titled "You have way too many gears". I think he's right, for most people. 2x5 is plenty of gears to ride your bike just about anywhere you want to go. We didn't lack for more gears back when that's all there was, when a "ten speed" was the pinnacle of bicycle engineering. We just rode our bikes and did just fine.
All that is to say that if it were me, I would keep the original configuration and enjoy the bike for what it was originally. I never understood the obsession with putting more gears on an older bike, even up to and including spreading the rear triangle. If you need (or want) more gears or a different configuration, that's why we have more than one bike.