[majormajor]

You would have to increase restrictions for the vulnerable group because if you allow them to mix at all (even at today's levels) with the "free spreading" group they are going to have much worse odds than they do today. Since you're intentionally trying to increase the proportion of sick people in the less-vulnerable group. People like the "grandma living with family with school age children" or the "30 year old immunocompromised cancer patient with a roommate" get fucked if all those people around them (and around them, etc) simply go back to normal and you don't more actively isolate them.

This might not be a terrible idea, though, if compared to a several-year-extension of what we have now... because over time, the cumulative probably of exposure for the vulnerable will just keep rising and rising if we stay at something like the status quo.

But... that's where things like vaccine and treatment development come in. If a vaccine makes catching it much less likely in 6 months, or treatment improvements make it much less deadly even for the vulnerable in six months, then it's worth spending another 6 months in the current situation.