I'm utterly terrified of that idea. If we didn't have the 22nd amendment historically, we'd have had Reagan a third time and Clinton a third time, and that just terrifies me. Hell, at this point I'd say limit the president to one 6-year term or even a 4-year term.
I like the idea of a single 6-year term. The President may have 4 full years, but he can hardly accomplish something meaningful past his first year. Second year, the midterm campaign starts and then one is already running for reelection.
Btw, I don't think Reagan would actually run in 1988.