Trumbo's value will likely never be higher. his low obp and high strikeouts are two problems. if pittsburgh is really willing to part with a quality arm, do the deal.
i have to think that whatever funk hamilton is in this year isn't permanent, and him getting back to his normal self this year or next should take care of missing trumbo. same with pujols.
Of the things you've mentioned, Sosh only has an impact (and it can be argued to what degree he has an impact) on fundamentals.
Dumping Sosh would not have any impact on the other things I mentioned (sucky bullpen, Blanton sucking, Pujols injury).
New manager wouldn't stop Pujols from being injured or Hamilton from sucking (though maybe a different hitting coach might).
New manager wouldn't stop Blanton from sucking.
New manager wouldn't have made our bullpen less sucky.
New manager wouldn't keep our base runners from making idiotic mistakes.
There's definitely an argument to be made for in game management decisions, but not sure it's enough to warrant a change.