You don't have to run a diferent manabase to put steam kin in, but I see your point about flying. I know you your subbing out combat tricks for burn because of removal, but the burn is not going to reach as much as the combat tricks. I think it's better to side more threats in, to make their removal more spread out. Experimental Frenzy basically says you don't stop dropping threats ever. They will need to board wipe almost every turn. Similarly, siding in lands and rekindling pheonix taxes removal.  You'll have to try it out to see if your sideboard plan gives you the reach you need to close the game. With four risk factor, it might be enough, and if it is, it's a great plan.

Love it. 100% yes.

Nice, I like your additions! Sky Terror is actually really great, especially with your combat tricks. Virtually unblockable, and will be such a blowout if they throw things in front of it while you have a sure strike. With Mentor, it actually might be just better than the boros challenger. I hear what your saying about the Torch courier, and it definitely might give you game in mirrors too. I look forward to get your thoughts when you test it. Definitely needs to be sideboarded out on the draw, as it will be hard to utilize at a disadvantage. In a similar vein, consider maximize velocity. Can be 1-3 of your pump spells, does a similar effect, gives you use of your extra lands in the late game like risk factor does, works better with mentor.

Tagic and Aurelia are probably the best cards in your deck. They will attract all the removal from your opponent. Having extra copies then are more attractive as the best top deck after they kill one is to get another. And you don't have a lot of card draw/selection so it's not super likely that you will flood on a legend.