I found an old hack for activecollab 0.71, installed it and it works like a charm in projectpier v0.8.
http://haris.tv/2007/03/31/prioritask-for-activecollab-071/
If the writer agrees maybe somthing to include by default in a next release. What do you think?
Note: I didn't try his other hack for tasks comments:
http://haris.tv/2007/02/28/activecollab-and-071-hack-for-task-comments/
haven't tried it yet, but it looks like a great enhancement!
Some code are used in Task comments
Patch works in .8.5.0-beta1, just make sure to use a diff tool to figure out the changes in the code.