There's a few BB7200 diagrams that stop at Melun out of Gare de Lyon as well on which the zonal tickets are valid; there use the very comfortable TER refurbished Corail stock. From memory I think there's four diagrams in the day; they use the same xx.19 / xx.49 paths in and out of Gare de Lyon as the regular fast EMU service - they can be identified in the timetable because they go further out than the rest of the services... I forget the exact destination at the moment!
Was just about to post this, although I suspected that either you or
87015 would have got there before me
Trains are Paris Gare de Lyon - Laroche Migennes, operated by TER Bourgogne.
About 35 minutes out to Bois-le-Roi, where you have a ~10 connection for a LM - Paris loco-hauled back would be my suggestion of a move.
Some loco-hauled services to Le Havre (those which stop before Rouen) also call at Mantes-la-Jolie, which is another good 30 minute run or so. Only thing is you'd likely be coming back on a unit (ok, not exciting but...) or a local loco-hauled service (Do not even think about it - lots of quite nasty places).
Suburb wise - North is generally regarded as worse (avoid anything with a '93' postcode (Seine-Saint-Denis).
94 (Val de Marne) is pretty nice, you can go for a walk down by the seine at Nogent-sur-seine (94 is also where I used to live, so maybe I'm biased?)
I'm also a fan of La Défense, I personally love all the different architecture.
On a weekday evening, take either the 17:05 or 18:05 loco-hauled out of Paris Est to Crouy-sur-Ourcq. You can then have a ~15 minute connection in sleepy rural (but beautiful) village for a unit back to Meaux. From there, you have a ~5 minute wait for a suburban train (non-stop) back into Paris Est.
You could also take the 17:12 loco-hauled out to Longueville (train terminates at Troyes), but you normally miss the connection back (or at least I did everytime, thank you TSR at Gretz-Armainvilliers) and so have to wait another hour in a fine but boring and rather forgettable town for the local service back.
PM me if you wish.