The problem picking a single mentor has is that the mentor you pick could well be a lazy one who doesn't really do anything. With the current system you at least have easier access to other mentors.
Back when I started playing Battlemaster the game was a lot easier to get into. All taxes came directly from the realm so there was no hunting for an oath or setting up your estate. You didn't have to rely on the lord caring enough to assign you to the right army, I think the ruler/general at the time had the power to throw anyone to the right battle group. So basically you were good to go the moment your character was created. No need to spend sometimes days doing confusing and trivial stuff.
A recent change made it so you don't need to be in your region to set your estate which is a good change it the right direction.
One of the problems I tend to see every time I create a new character is lords giving out really crappy oaths. Now, I know better than to accept such offers, but new players probably don't see that 10% of a rural region isn't going to give them much. So they end up with an oath that gives them 10 gold each tax. Doesn't do much to encourage playing when you can't afford to do anything. Would be nice if an oath offer from a lord included an estimated gold income with the percentage offered and maybe even warned the player on low offers that according to the estimate the income wouldn't even be enough to pay his current unit for a week.
So yeah, anything that makes it easier and faster for new players to get into the action would probably help keep them interested and with the game.
