Develop their relationship slowly, of course. Egon's not going to move very fast in something so patently illogical. But develop it!!!
RGB got stuck in a rut because it was a cartoon that became more and more aimed at kids after JMS quit as Story Editor. Some of the prevailing “wisdoms” in American cartoon writing thought are: “Romance is boring when you want to tell action toys to eight year old boys”(which is true, unfortunately, for the most part) and especially “The Status Quo Must Be Maintained” (More a judgement about the percieved short attention spans of kids and the crassly commercial urge to sell it into syndication–if the Status Quo never changes, it doesn't matter what order the episodes run in)
Then GB2 threw the whole Louis Tully monkey wrench into things. To their credit, the RGB writers vetoed that–two episodes that ran after GB2 testify to that: “The Ghostbusters Live From Al Capone's Tomb” (Janine kisses Egon at the end, in full sight of Louis) and especially “Janine You've Changed”, the latter of which actually held the promise that Egon and Janine were finally going to be allowed to happen.
Then XGB came out and restored the old same “unresolved” Status Quo from RGB as though “Janine You've Changed” never happened. Dammit, Egon and Janine weren't the stars of XGB anyway, so how much different would it have been if instead of popping up after not seeing him in years (“Darkness At Noon”) she'd popped up to, say, bring him some paperwork he forgot and she rescued in time “before the Twins drew Venn diagrams all over them in crayon”? almost no difference at all. “The Crawler”, “Temporary Insanity”, and “Rage” would've needed rewrites, but that would've been all.
My main hope is Red's oft-repeated mantra that the new comic “Is based off the first movie”. Don't move too fast, that wouldn't be right. But move it. We've been waiting a long time for someone to do it right and do it justice.