Honestly, much as I love most aspects of the Superboy mythos, I could easily do without the Smallville "origin" for Lex's vendetta. But in general I think Unlce Morty's bullpen was on the right track making the two roughly the same age.
I don't think the Smallville origin is essential, either. At least not the "failed experiment turns Luthor bald" part. Maggin made that origin believable by adding well written subtext to it, but a large degree of fans probably would (and do) overlook that. Still, you could always have the two in Smallville without that origin--Superboy and Lex start out as friends, Superboy gets more attention, Lex begins to hate him. Kind of like Darius Dax from
Supreme. Lex could always lose his hair later--maybe naturally.
Plus, he just looks so cool in that purple spandex battle suit! Can't pull that off when you're 60!
Agreed. Imagining a 60+ Luthor in spandex is the stuff nightmares are made of--not a pretty picture.