I think you understand things right, but I would not sweat it: I never recruited a general in BI. BI is basically a standalone campaign - you should be able to run it just by sticking your BI disc into your computer. I found it quite a refreshing change from RTW - the Western Romans, in particular, I found fun. You can see a write up of a PBM campaign we played as them:

https://forums.totalwar.org/vb/showthread.php?t=60372

If you want more of BI, I strongly recommend Goth's all factions mod. You can find it on the Rome Total Realism forums.

If what you are looking for is an improvement of the vanilla RTW campaign, I can't recommend too highly Rome Total Realism: Platinum Edition and Europa Barbarorum. They take the original RTW and give it a complete makeover. It's still recognisably the same game, but is much richer in historical detail and has more rewarding gameplay.