Well, I don't know how I avoid spoilers, but as far as possible I do 
I wouldn't miss Mary either. She was ok when Norris was in it, but on her own she is just annoying.
Debbie would be good behind the bar, as would Sally and Tim in a reprise of Annie Walker and Jack, with Cassie as a barmaid.
A playgroup or nursery might bring in some storylines as there are lots of young children, and maybe an adult education centre (although they are being closed down rather than opened). Something akin to the WI or U3A could work, too. The Weatherfield Institute? There could be struggles for leadership, comic incidents with cookery or flower arranging, exam passes and failures, a drama group with a Christmas panto. They could let us see the Red Rec, with maybe a bowls club or something for the older characters.
All low stakes and cheap enough, with more realism than the numerous lawyers and the overworked doctor. Or two hairdressers for a few houses, come to that.