Char Aznable is basically Gundam's Darth Vader; masked ace pilot with a mysterious and important past, that becomes a big defining part of the conflict despite not being a leader, basically as contrast to the also-ace-pilot hero. Nero being brought in for this story is fitting, because he himself is a bit of a Char riff in his aesthetic, overall personality, and contrast with Cid.
When you hear about 'Char Clones' in Gundam fandom, it's not actually referring to clones, but rather that Gundam stories have a tendency to introduce characters that fit the same role (because why neglect what works) and put their own spin on it. Zechs Merquise in Gundam Wing was probably the first to so clearly try to recapture that magic, 00 has Graham Aker, Iron Blooded Orphans has McGillis Fareed, and even right now Witch from Mercury is doing an unusual spin with Prospera Mercury.
...that said, there is one 'Char Clone' that is a damn near literal Char clone, and that's Full Frontal from Unicorn. The fake Valens is very clearly combining elements of Full Frontal (who's also a person heavily altered to become a double of Char, trying to galvanize remnants of a fallen fascist empire) with elements of the original Char Aznable, particularly in Gundam The Origin (where he attends military academy under a false identity, wearing shades because his eye color gives away that he's not who he's claiming to be). And honestly, I think it fits for who Valens is--who ironically isn't much of a Char himself. This absolutely reads like a plan he would've been all-in on.