"What would concern me for the firm's future is this: [lack of investment and asset allocation expertise, and stupid M&A."

I agree. Warren was the best investor and asset allocator of all time, and he did not do M&A for ego. His shoes will be impossible to fill. More expertise on the board will not solve the problem of losing Warren.

I did a quick and dirty calculation to illustrate your point about how important investments are:

Berkshire asset, percent of company by assets, trailing 10-year return

equities, 25%, 15%/yr
T-Bills, 25%, 4%/yr
Other (subs), 50%, 15%/yr
Total, 100%, 12%

It would take a large shift from T-Bills to equities, or preferably to subs, to change the total value growth rate. For example, converting half of the T-Bills into subs or equities earning 15% would only increase the total return from 12% to 13.6%.

Just another point about value growth... the period in time makes a huge difference. During the '80s and '90s Berkshire's BV grew 29% annualized. Since then it has grown 12% annualized. Warren was in charge during both periods. Even the best are not immune to the times.