He could incorporate air dashes, Roman Cancels and if Sakurai's crazy enough he could make Sol's final Smash an instant kill, like happens in his games lol
Also he has Dragon Install as a transformation. That or roman cancels could use a meter.
And while some of his special moves are somewhat similar to Terry's visually speaking, Gunflame would have less range but taller hitbox, maybe more powerful than Power Wave. His specials could be:
Up Special - Volcanic Viper (0:25 in the video), if Sol hits then he can do Knockdown by pressing the button or entering the command input a second time
Front Special - Bandit Revolver (0:04), but if you charge the move Sol will do Bandit Bringer (0:17)
Back Special - Riot Stamp (0:36)
Neutral Special - Gunflame (0:07)
Down Special - Fafnir (0:48)
Dragon Install (1:03 in the video). It would be very cool if the song that plays changes to
Ride the Fire as happens when he uses Dragon Install lol
I wasn't active in speculation before Pit was added but that doesn't surprise me a lot. Sure, I greatly doubt he had the same support as K. Rool or Ridley, but I can see him being a frequent request even if he wasn't the most popular one.
I'm sure a good amount of his supporters back then didn't played the original Kid Icarus or the GB one but I guess that the concept of an angel and all that was enough to convince that people.