I have an idea for a compromise.
*Foot note.. I'm just pulling this out of my

as I know very little about Collective Bargaining and the normal way it works.
Put Collective Bargaining agreements back in
with a caveat.
Leave Collective bargaining in as is, if they agree to the other terms(Increase in what they pay for benefits, pension, etc.) for two years.
In two years we will then, through collective bargaining, look at the state of the economy and update the agreement accordingly.
Under this agreement, every Union member will get a "re-vote" over the next 6 months on whether they want to still be unionized or not and that agreement will stay in place for two years, until another vote will be needed.
I'll even throw in removing the voluntary union dues from the bill.