Yes they have roles - I said as much - but they are secondary compared to the effect they could achieve in DBM.
things I use Ps for in DBMM:
- holding difficult terrain
- shielding heavy troops from shooting and enemy ps
- opposing enemy Lh if I have nothing better to do it with
- flanking/lapping
- providing rear support where allowed
Not so different from DBM really - but there are things that were "important" in DBM that are no longer there
Things I might be tempted to use Ps for in DBMM:
- disrupting heavy infantry - especially pike (since pike don't count rear ranks against them - but I suspect this will be like Lh vs Kn in DBM - superficially tempting, and occasionally it works, but most often you jsut lose all your troops to no effect)
Essentially completely new - Ps vs heavy infantry was pretty useless inDBM - even with 2 overlaps the heavies could get 2 or more ranks so was normally at factor 3 or more. The Ps wouldn't get killed, but they wouldn't actually achieve anything either - there was no realistic possiblity of actually disrupting the other guy's heavy infantry.
Things I can no longer use Ps for in DBMM (compared to DBM), or no longer want to use them for (ie they can be used...but it's a waste of resources now)
- holding a flank on their own without terrain cover or heavier troops in support
- preventing enemy movement
- hang around in the open as general purpose reserves, easy-to-manouvre irregulars, or something I bought just to use up the points
IMO the removal of these
2 3 roles is the big change that puts Ps into its proper place