I'd be all for it. I loved John's old series in the 90's. Well, except for the middle. Started and ended strong, but the middle? Not so much.
Anyway, I think there's a lot of potential in the idea. John is more than DC's Tony Stark; he's his own, very unique, man and with the right vision a solo series could be mind blowing.
But I dont see it happening anytime soon. DC tried this kind of concept with Batwing, and that title isnt selling all that highly. In fact, isnt it one of the titles everyone is expecting to be among the next cancellation wave? And aside from franchise connections and hometowns, there is not a high degree of differences between Steel and Batwing. At least not enough for the casual fan to care about.
But it could work. The problem is that you have to really push things in a new direction. If people want a guy in a power suit they can read Iron Man. If they want someone wearing an "S" on their chest they can read Action. So Steel has to deliver something we're not getting anywhere else. That's the rub.
If it were me, I'd go to Ellis, or one of the other WildStorm guys who made that company more than the bad caricature it started out as. Steel, in order to sell, has to hit that sort of bleeding edge concept and (actually) new direction that made books like Authority and Planetary so great. It has to be more than "Iron Man with a red cape."
To that end, I really hope that when we see John next, he's upgraded his armor to something League worthy. One of his great downfalls (imo) was that his armor never really improved. He never reached the level where he could stand toe-to-toe with his JLA peers. We saw minor tweaks here and there, but that was it. And to stay ahead of the techno-curve, John will have to build/upgrade suits constantly.