The advantage to a dedicated pistol is not having to swap the uppers on your receiver. It's not a major operation, but I just couldn't wrap my head around a perfectly good upper slide/barrel assembly with no pistol under it, so I built a budget receiver and made a dedicated .22 caliber 1911.
As far as I know there is only one .22 conversion for the 1911 that locks the slide open on empty: the Advantage Arms. I think the lowest cost conversion is still the Ciener, but only a dedicated masochist would buy from that guy today. Mine is a Ciener, but I bought mine from Brownells, before they stopped carrying his products. The Ciener and the Kimber conversions do NOT lock the slide.