Replacing the discussion system
I agree that the many pages created LQthread should be convertible to normal MediaWiki subpages (merging their titles and regenerating default signatures and dates).
However note that there's a problem in how many subpages we'll need and how to preserve the threading: we can't merge all them into a single subpage without exhausting some limits, or breakign the threads; additionally, if we merge separate threaded messags into the same subpage, there's the need to preserve the indentation, and their relative order. Some existing threads have many levels of replies, so in a first step each message should be a separate subpage, then a default parent page could transclude them (within indented blocks). Note that in LQthreads, replies may have different titles than the message they were replying to in the same thread, so the titles of each thread cannot be a normal Mediawiki section header, EXCEPT the top-level where it could be used as a section header in the wiki subpage (with == for normal second level) (for all other levels, it would become a === for a unique third level, the indentation in the parent page transcluding them could insert the indentation needed, using for example an collapsible box template: the header of the collapsible box would be the signature and date).
Even a single LQ message in a talk page would be come at least 2 subpages: a parent subpage for the presentation and containment, containing a collapsible box template.
Such conversion tool would not just be for this wiki but for any Wikimedia wiki where LQ is about to be deprecated, before it is finally uninstalled. Idelaly it would require the use of some external bot trying to make the conversion, it would need parameters to set the source LQ talk page (where LQ thread were attached), and the target pagename (not necessarily the same, and possible with an editable subpage name instead of some default "/old Liquidthread messages", as user pages have various ways to organize their archives.
Once the user owning the user talk page (or the community otherwise that manages a content talk page) approves the conversion, the old threads could be deleted (but there's an issue to preserve the history for copyright reasons, so most probably they would be frozen: all futher edits or additions would be in the standard mediawiki (sub)pages).
Finally the conversion bot should be made part of DiscussionTools, which would also have ways to manage/reorganize archives.