Would like to travel south by train from Maastricht, Netherlands to Toulon, France (bypassing Paris altogether). I'm aware this is a long trip but am wondering how long. Is it scenic and what would be a good mid-point for an overnight stay enroute? Thanks!

Hate to tell you but all roads, er tracks, lead to Paris, basically. Even if you don't plan on staying in Paris, you would have to at least change trains and probably stations.

Look up on the sncf websiste for more info. Offhand, I would think you would arrive at Gare du Nord and leave from Gare de Lyon.
Paris would be my choice for a stop over, though I suspect you may be able to make it in one day if you start early enough and make good connections, and use the high speed TGV of course.

Good luck. Maybe others who have done this specific route can help you more. If not, go to sncf on line.

Never look at an sncf site if you are looking for long distance connections!!

The German site shows it all.
No problem. Your best bet leaves at 7:09 in the morning, a change in Liege-Guillemins, another change in Bruxelles-Midi to a TGV which goes direct to Toulon. That train will stop at Lille, CDG (but not within Paris itself), Marne, Valence, Avignon, and Marseilles, before getting into Toulon at 3:47 in the afternoon.

Want other options or information? (although it won't price it for you):

http://reiseauskunft.bahn.de/bin/query.exe/en

The train ride can be anywhere from 8 1/2 hours to 15 hours, depending on the route.

Bypassing Paris (sort of) is the following, which takes 8 1/2 hrs and you must leave Maastricht at 7:10 a.m.:
Maastrict to Liege-Guillemins (change trains); Liege to Brussels (change trains); then Brussels to Toulon, with stops at Lille, CDG, Marne La Val Ches, Valence, Avignon, Marseilles, then Toulon.
Three trains, 2 changes.

Thanks so much for all your help. I should have been more specific. The route we were hoping to use would take us from Maastricht to Luxembourg, Nancy, Dijon, Lyon, Avignon and then Toulon. I'm betting this would take days...but hope not. We want to see a part of France we've not seen before but our time is limited.

Fastest trains with least stops, from a search on sbb.ch

Masstricht 14:09
Liege 14:41
Luxembough 17:45
Nancy-Ville 19:22

Next day, Nancy-ville to Toulon on TGV 5148 (with stops including Dijon, Lyon, Avignon, Marseille) 7:33, arriving Toulon 14:09

Takes exactly 24 hours. Or there's the same connection from Maastricht to Nancy-ville exactly 2 hours earlier if you want to have more time in Nancy to find a hotel.