And for your other points, entering singly would set you up with an array of team mates based on the BV of the mech you chose, like in WOT. If you took an Atlas that was pimped out, the game would assign you to a match with higher BV, and place you as the "heavy" of your lance.
If you entered as a partial team, the system would look at each mech independently and so assign you to a match with another similarily kitted lance (like a partial team of 4 atlases would face another team of 4 atlases).
If you entered as a full team, you could divide the BV however you wanted with your team mates. If anyone was a **** and started sucking more than his share, you could simply boot them and not play with that person anymore.