Preface: I am not a compiler engineer at all, so I'm just spitballing silliness here.

Avoidance of type feedback counters and such. Get LBBV to clean out the redundant type checks (Higgs proved this well, avoiding something like >90% of them) and produce a format, perhaps a high-level bytecode or just an HIR, that can be used as an input to start a method-level JIT compilation.

So, LBBV gives the quick and easy basic block compilation and cleans up the very easy stuff but leaves enough information so that a follow-up compiler can still use it as input.