Good thoughts. Reflectors all have a set multiplier for damage and knockback (see
listing of specific multipliers here), and we could technically test that with Gordo to know optimized reflect moves, kill %s, etc. Honestly I don't think going through all possibilities would be worth it - Gordo reflects aren't what win high-level matches, but there are a few specific matchups where it's very useful.
Offhand I know of two: Fox/Falco and Villager. Fox's reflector multiplier is 1.4x, and I've gotten a OHKO by hitting the reflected Gordo with a Fsmash and an...UpB (totes hilarious). And Villager's Pocket multiplier is 1.9x; we all know that hitting a pocketed Gordo back = OHKO on Villager. Good luck with that, you'll need a lot of precision and timing to beat out the inevitable Lloyd Rocket as well. But the good news is that in both matchups, the reflected Gordo WILL OHKO them, and usually won't OHKO us.
Anything more? Those are the main two high-level reflector-invovled matchups I've have experience with. The Nesses I've played don't like to risk the Fsmash reflect, and there aren't many Pits around here.