Folding BAM into BRK kinda makes sense for both. BAM can put BRK cash to good use, especially since a lot of stuff is capital/organic/M&A intensive, and has loads of operational expertise. BAM doesn't have to be as dependent on various funding source.
But my sense is that unless BRK gives a great deal, BAM is more than happy with whatever it's doing. BAM might get some benefits under BRK, but it can do any deal it wants with what it has. And like BRK, BAM seems to take enormous pride with working with their investors.
There are also lots of different insider/controlling shareholders (from what I understand) to work out a BAM sale.