The MiG-23 certainly had a lot of potential, see the later variants even with the VG wing. Drop that one and it can only save weight and gets better.
If you want to get a glimpse of what it takes (for an alternate Mig-23) to go from VG to non-VG (or reverse) see the Mirage F2 and Mirage G.
The closest the West ever came from a Mig-23, since the Tomcat, Tornado and F-111 were larger, while Vickers 580 series remained paper bound. And Viggen was delta canard.
The airframes were mostly identical, minus the wings. Both flew very well and alongside each other - between November 1967 (when the -G flew) and May 1969 (when the F2 was retired).
Can't think of another example, that's the LEGO side of Dassault. Rockets are not LEGOs, but Dassault combat jets truly are.
A swept fixed wing MiG-23 would looks like a scaled-up F1 except with a far more powerful engine than the Atar. You know, a modern turbofan with 10 tons of thrust.
Wait, Dassault had plans for exactly that: that was called the F3, with a SNECMA TF306E. Ironically, in April 1967 it was dropped for a 0.80 subscale clone small enough for an Atar 9K50, called: the Mirage F1. Which had flown as a private venture in December 1966.
And of course, third time was not the charm, later was a F1 with a M53.
[One could draw a family tree all the way from Ouragan to Rafale, encompassing the Mirages, Etendards and even the Mystère 20 bizjet along the way - since its very name, and wing was derived from the Mystere IV. Which is truly the nexus of the whole thing: Mystère before, Etendard and Mirage and bizjets afterwards. Unbelievable, but I digress.]
