sorry if something like this has already been discussed, I havent been active in the forums so far due to lack of time, but expect things to improve.
From what I understand, players can pledge to a house, go solo, or join a merc group created by another player. What about paint jobs? I suppose there are custom jobs that are purchased with real money, here's a few ideas:
There should be a few generic paint jobs, at least one for each faction, that are free to use of course. I think choosing House Steiner for instances the player should be restricted to Steiner specific paint jobs.
Here's my sugestion to payed content (paint jobs): each house has a number of known regiments or units, although I dont know how those are being handled, an ideia would be to allow the player to purchase for instances the 1st Royal Guards paint job, and thus be identified as belonging to that unit for as long as the player uses that paint job. Or another way of looking at it, if a player wants to join one of those well known house units, he pays for it and gets a new shiny paintjob as a bonus

As I dont want this idea to get too much heat from the players that are hoping to have access to such features without paying for them, an option might be to allow a player the rights to buy a command rank in one of these units (doesnt mean he'll be THE commander), and then that player can recruit others. The recruits will get access to the paintjob and listed as belonging to the unit and serving under the commander that recruited them, with the option to leave any time as each player can only have one commander.
This is a possibility to allow the house units that are already active in the forum to have a future in the game, as long as the respective commanders have the means to buy the rights described above, and their desired units exist at game start of course. And I believe this needs not be restricted to house units, but well known mercenary units as well.