That BV imbalance could be adjusted upwards slightly for contracts versus the Clans, where they get a +10% or +20 BV edge, on top of the random +/- 25% adjustment to whatever the normal BV balance happens to be for the battle. Facing 5:1 odds against you isn't an "uphill challenge", it's suicide. Clan bidding would normally pare that down to a modest advantage, not a tidal wave.
The Clans should NEVER outmatch the IS in terms of tonnage, they've already got better piloting/gunnery skills plus better equipment, plus the 'Bot doesn't suffer from the Clans' biggest tactical limitation: Zellbringen. If a Clan commander can't expect to win with equal or near-equal tonnage and better skills and tech, or less than a 2:1 advantage in BV, he or she is clearly incompetent or timid, and would soon end up facing challenges to his or her position. Basically, the force balances in the scenarios need to be reworked in AtB, because far too often it's nonsensical.
Additionally, hovertanks should never be required to deploy on a heavily wooded map (I had one battle where there weren't enough clear hexes to even deploy), nor should wheeled or tracked vehicles be forced to fight in a swamp, especially a "break through to the opposite edge" mission when there are NO clear paths across. Odds are, you can't complete the mission even if nobody is shooting at you, and far too often I've seen the 'bot simply park because there's no way through. At least the human player can sometimes clear a path by razing the forests or setting them on fire and waiting until the fires burn out. Basically, for the commander running those units (whether player or 'bot), you know in advance that you simply can't go there, so why are your units fighting there? Reloading a previous save takes far too long, and having to do so 5-10 times in a row to get a mission or battle that's even playable gets old in a hurry.
On the other hand, if the map generation algorithms are tweaked, with a configuration option to force at least one traversable path across the map, it might solve a few of the problems for combined arms forces.