1. A BV target for the mission? I mean yes, of course they have to, otherwise the game is unbalanced towards the player with more BV.
2. So I have an idea, but it really depends on our Noble GM and his Unlimited Armies of DOOOOOM!
Split forces. Each player builds two forces, Offensive Line and Defensive Line. The two forces have to meet a certain combined BV threshold as well as fall within a certain range. These units deploy differently, OL deploys during the movement phase of Turn 1 as normal and their role is to move towards the primary objective and secure it. The DL deploys during the movement phase of turn 2-3 (depending on the scenario) and their job is to stop the opposing OL.
So if our BV Limit is 15,000 and the OL has to be 8,000-9,000 BV then the DL has to be between 6,000 and 7,000 BV. This can vary by scenario and mission. So if you have a Recon Mission, you might only get 5,000 BV (or less) but your opponent has an Assault Mission so you get 10,000 BV for your DL.
Where Joel comes in is the Defensive Line. Since he knows the scenarios beforehand he can bring some pre-generated Defensive Line forces for players who either don't have enough units, aren't confident in their force building skills, or think they need a hard counter for Hellraiser ;). From a fluff perspective the forces that Joel provides would be the regular forces from the organization that hired the Player's mercenaries.
This lets Joel ease the introduction of new players (he can over BV them if they're going up against a particularly tough veteran), give players who don't have good list building skills experience fielding forces that are both better (hopefully) and different than what they would have put together themselves and allows him to have list counters available if necessary.
With two forces per side and (theoretically) larger forces we'd probably want go up to larger sized maps.
3. I'm not really sure what's wrong with the current force creation rules, other than after a new player gets some experience they want to swap out their entire list... but that's not really force creation issues, it's lack of experience. Which is hopefully mitigated by #2.