Ideal lineups would follow skirmish trends which apparently are influenced by the 'pro' scene (which I only watch if I want to fall asleep).
Basically, mostly heavies (tier 8 mediums are bad... only a few are used in niche roles) with lights providing eyes and playing the role that mediums play at tier 10. No arty and no TDs. Heavies tend to mostly be IS-3s and 110s with a handful of 50 100s. Lights at 8 are Ru and 13 90 (though I've heard murmurs that the 54 light has potential... but stay away from the 49, it's rubbish). Tier 6 light would probably still be the T37. In skirmish the ideal all around setup tended to be 2 lights, 2 50 100s, and the rest real heavies. This setup could work on every map though on the open maps you listed a larger force of lights might be ideal.
Edit 1: Just thinking out loud here but maybe 2 tier 7 lights instead of an 8 and a 6. Haven't looked too closely at the stats to see how the Walker Bulldog compares to the 8s.
Edit 2: To elaborate further. No arty because of the limited number of players. Against a good team they'll simply swarm you at the point of contact if they know you have arty and good players know where to position to minimize arty strikes.
TDs are less valuable because of the mobility at tier 8 (the heavies mentioned above are all fairly fast) which means good teams reposition quite a bit. Such gameplay basically goes against what a TD is about. Certainly you could make it work, though. In one skirmish battle I remember running up against one of the good Asian clans and they ran a 50/50 mix of lights and TDs. The lights zoomed up to a key position on the map with the TDs in overwatch. Their lights were also all autoloaders so anything they met died and trying to dislodge them from different angles ran into the TDs. Takes a good team to pull that off, though (and the only TD that comes to mind that might work is the roomba given the turret and dpm it has).
Given the poor balance of the game at tier 8 lights are basically the best mediums. Very similar hps, same if not better dpm, with much better mobility coupled to light camo mechanics.
Edit 3: Prok, Steppes, and Murovanka could actually work with the light/TD combo. Spots on both for lights to hopefully get into key spotting positions and passive scout coupled with terrain that still allows survivable active scouting. Line of sight and cover for TDs at max view range and draw distance to support.
The other maps would be more ideal for the traditional 2 lights, 1-2 50 100s, rest heavies.
Edit 4: A Charioteer would be another TD that could work. Firing HESH, which will reliably pen everything but the heavies, it has higher dpm than the roomba with the 128. With normal rounds it still has good dpm and it's fairly mobile with a turret.
Edit 5: Did some quick math comparing the dpm and hp comparison of the TDs facing off against the heavies. It's neck and neck, really. The heavies at least should bounce once in a blue moon. The TDs, if spotted, won't. The safe route with some cushion is the traditional mostly heavy lineup. I'd save the lights/TDs for a team that has some cohesion or is made up of better players.
Edited by Skywalkre, 11 April 2015 - 2020 PM.