That's a good idea, but the leftists know what would happen if such a bill became law. Imagine Virginia wanted out and Maryland stayed in. Maryland would get a lot of new "immigrants" seeking health care paid for by somebody else (including some who are in trouble through no fault of their own, but are going to take a lot more in medical services than they pay for). Virginia might get a different kind of immigrants from Maryland: entrepreneurs.
I'm not sure how much wealth Maryland gets from people working in DC, but I don't think it's enough to make up for such a shift.
I believe those states that remained in collectively would not be able to pay for it. So count on the leftists to either block the bill, or amend it so that states who want out pay for it anyway.
My national ideas are not revolved around trying to make my neighborhood a better place to live at expense of the country. I am the first one to call the claim that ‘my tax cut pays for itself’ Republican Koolaid. (No I am not giving it back.) I like the opt out idea because I think it it is arrogance for the Federal government to micromanage states. If lib states want Obama-care, who are we to say stop them? and vice versa for conservative states wanting out? If CA wants more poor, let them put up the welcome signs.
It will take a lot before this area of MD is hurt economically. This is one of the richest areas of the country due to federal $$$$.