The most interesting choice would've been Colin Powell, with all the caveats about getting him to run in the first place. While it's probably more likely he'd run a pretty managed, by-the-book 90s Republican campaign, part of me is curious what happens if he clashes sharply with the newly-dominant conservative faction. Say it's him against Pat Buchanan, who did pretty well IOTL. ITTL he's got not only a bevvy of semi-closeted racist feeling to draw upon, but in Powell a (potentially) genuine Rockefeller Republican trying to buck the party's trend line. If Powell were to lean into that contrast, the fight could be pretty epic, though likely damaging to the GOP.
Assuming Powell wins (which honestly he might not; 2016 has us all recalibrating likelihoods) he's pushing into Third Way territory domestically and maybe even pushing past Clinton to call out some of his shortcomings on poverty. But mostly he's hoping to make this about foreign policy. Clinton plays the experience card as much as possible. Perot might not run as Powell really undercuts him on most issues except trade, and the horse has already left that barn.
Does Buchanan run as a spoiler? I would flip a coin, honestly. His funding would be set for the duration if he fully embraced the religious right. But we already kind of know what happens without Pat Buchanan, as a lot of conservatives stayed home for Dole. His presence might even have a positive effect on Powell's chances if Powell's got a ceiling problem and a strong third party lowers the number necessary to win.
Do African Americans break for Powell? God, that's a tough one. Jesse Jackson still carries a lot of weight at this time, and Al Sharpton's right behind him. My gut says they rally behind Clinton and defections are kept below 15%, but if they don't those numbers could spike pretty high. Maybe 50%, maybe more?
I think it's a close race. On the fundamentals you give it to Clinton, but it's a possible sea change election with Powell in the right frame of mind and those are unpredictable.