Since it's widely possible that Dr. Wily came back as a cyborg of sorts (but no less half-brained) in Megaman X, so here's what I thought should have been done.
In Megaman X2 as Serges, Dr. Wily could actually be the second to the last boss to Sigma. So maybe he tries to take over Sigma's organization as Serges being the leader of the X Hunters. So make him the second to the last boss who has Zero's parts. So he finally admits to Megaman X something like, "Don't you remember me?" type of talk. Instead, we had Agile as the second to the last boss (if Zero's body parts were found). Then maybe in Megaman X5, he attempts to use a new version of Gamma only for Sigma to get the new body.
In Megaman X6 he should return as the main antagonist of X6 instead of Gate. I just thought why not make the fortress bosses as first final fight with Hi-Max then Gate then Isoc (who should reveal himself to be a fully mechanized Dr. Wily). Isoc could pilot another battle Wily machine. Then of course, for a rather karmic end to Dr. Wily, he revives the supposedly dead Sigma to get revenge on Megaman X (or Zero) then Sigma says, "Well thanks for building me my body back then but I must say farewell." Then Dr. Wily is forced out of the way but he manages to survive yet again.
Maybe in Megaman X7, he could again play another vital role. Pissed off at Zero, he revives his other "son" Bass and renames him Axl. So maybe Axl is still the same pompous rebel robot. I just thought maybe he could be the mastermind of the rebellion only to discover Sigma is just too powerful. Then maybe as the leader of this Code Red army, he could actually be inevitably destroyed. I guess reviving Bass as Axl would prove he's not gotten any smarter despite his high IQ.