So pretty much anything is possible? Cool.
Hxh system allows for a lot of bullshit, that's why i love it. I like transmutter class because you can keep it simple, though...
In your case you can, like
Buy fireproof vest, emit your aura a centimeter away from you and turn it to fire
Or
Make your aura gasoline and walk around with something that makes sparks
Or
With manipulation you can alter other stuff's temperature to make them burn
There's so many ways of doing different stuffs it's pretty hard to classify the character's nen categories
I thought knuckle was a conjurer because of potclean but he's an emitter, for example, both classes can do that skill happen though :p
Transmutters happen to have the most vanilla powers and use them to do amazing stuffs, they are like the rogues of hxh, which is why i like them, you can have a tax dealer with lots of convoluted skills, or have very tricky systems to manipulate people using needles and mobiles, or... just make your aura a freaking thread like machi and use it in thousands of creative ways instead :p