In California, we have to have 10 round mags, and a bullet button (modified magazine release that requires a "tool" --an allen wrench, bullet tip, or a set screw installed on a spare magazine -- to release the spent magazine). With the advent of the magazine-mounted tools, it's really not any slower than a normal magazine change. The only limiting factor is the low-cap magazines.
If you do that, you can have all the "evil features" you want (bayonet lug, collapsible stock, pistol grip, flash hider, etc...). We're pretty close to knocking down the semi-auto rifle ban entirely, after which we will have a shot at taking down the low-cap magazine law.
In any case, a lower like this would be worthless in Cali, or worse, would get you an all-expenses paid trip to state prison. We essentially HAVE to have off-list lower receivers, which are, de facto post-ban.