(welcome to Tikiwiki community
Some of the issues you talk about can be implemented right now using (a maybe slightly modified version of):
- Forums, to discuss subjects, and allow users to vote on topics. Besdies, you caould have several consecutive forums, and once a thread get enough consensus (through user's votes), it can be moved to the forum of the next phase for further discussing how to implement it, when, etc. See example of possible process at: http://vivarto.com/tiki-index.php?page=Nornorna
- Trackers: this feature also allows rating on items submitted, comments from users on a item basis, etc. This a very powerful feature (but also difficult, maybe, for newbies).
- Wiki pages: they allow rating also.
See documentation for their usage (or request help here if you get lost in documentation, for instance, looking for some of those issues)
Tikiwiki 1.9 has most of this features that you need. However, Tikiwiki 1.10 had some improvements on most of them.
Hope this helps.
Cheers, and thanks for posting your message and holding that initiative!