Customize --pow-start

[Mukrosz]

Is your feature request related to a problem?
Current --pow-start executes external batch at the time of block ..99 which isn't preferable because latency is king

Describe the solution you'd like
Is it possible to add a further customability to choose which block to execute the external script? Say block 97 ?

Describe alternatives you've considered
none so far

Additional context
Thanks a ton for your efforts