Certainly no harm in asking and RPoL Development is exactly the right place to do so. :>
As has been noted, RPoL already has the ability to multi-quote (hit reply and then click on quote in each required thread in turn, does require some scrolling) though not in the proposed format (select the ones you want then 'quote all').
Personally I would never use such functionality ... but by the same token, I wouldn't be against it either (unless it made the interface more cumbersome). So my vote is 0 (ie abstain).
Here's a link to an earlier discussion on the same subject:
link to a message in this forum