Well, explaining everything I'd do would result in a pretty long post so I'll just keep it short. I put a ton of thought into this a year or two ago when I made the same thread.
We're going to "Miles Morales" the hell out of Firestorm. Forget the Nuclear Man, we're going to dig deeper and explore some cutting edge science with the Quantum Man. The Firestorm Matrix would play a big role; its a unifying, fundamental force in the universe responsible for molecular bonding; that's a huge thing to explore and be responsible for. Calabi-Yao manifolds, gravimetric waves, FTL theory......there's so much cool stuff happening in science these days, and Firestorm would ride that wave. What the Speed Force is for Flash, the Firestorm Matrix should be for Firestorm and its a realm worth exploring. Especially the cities inside it. Oh yeah, those would be weird as hell.
I'd play up the importance of Martin Stein in the science community, making him the head Director of STAR Labs and the go-to nuclear physicist on earth. I'd take Ronnie and Jason both out of it and introduce a 14 year old character to be the other half of 'Storm (playing up the generation gap with Martin); one vaguely based on Jax from the CW shows. Basically combining the best elements of Ronnie and Jason into one character while creating someone unique. Hopefully that would be enough to bring the divided fanbase together, and neither Jason nor Ronnie would get abused or killed off. They'd both be alive, out of the hero game and happily living their lives, both likely looking at marrying their longterm love interests. I'd use them as occasional supporting cast members, just for the respect, yknow? But I dont think nostalgia would serve Firestorm very well, nor would bringing the Ronnie v Jason fan wars back to the fore. Jax, as a "unbiased third party" might be what everyone needs to move forward. (yeah, I have my doubts about that too).
Lorraine would be a hotshot young senator, torn between her friendship with Stein and her desire to see the Matrix in the government's hands as well as her fear of a child possessing that much raw power with so little oversight. Some shades of Marvel's SHRA there, but without the character assassinations.
Half the time, Martin uses Firestorm to explore the Matrix and perform science experiments. Jax finds it boring as hell. The other half of the time, Jax uses Firestorm to fight crime and be a superhero, which Martin finds terrifying and a waste of their potential.