Jet Flaming Gatling Gun with Haki
Jet Blazing Elephant Gatling Gun with Haki
Gomu Gomu Bomb (like Kamehameha)
Jet Gatling Gun Fireflies with Haki
Giant Bazooka Bomb (like Ransengan)
Jet Gatling Red Hawk with Haki
Jet Gatling Higan
Giant Emperor Hammer
Jet Gatling Hiken
For some reason i can imagen an gomu-gomu firethrower, with Luff taking air and then letting fire out of his ass...
Any or all of these moves would be fine by me. I would like to see a gear 4th/overdrive. I imagine Luffy using gear 2nd but going into overdrive with some of his limbs engulfed in flames. This would definitely make him Admiral level.
If Luffy did intake the Mera Mera, I wouldn't want him to be intangible like other Logia...not that it would matter. I think Japanese fans would go ape shit of Luffy having a second power. American fans...not so much.