MSE is a Q&A site but this proposed one follows a similar path to Puzzling SE which isn't really Q&A
For example
A question on MSE could be something like 'How to integrate this expression' whereas a question on the proposed site could be 'Prove that this function has five stationary points' but the asker knows how to do it
Proposal: Math Challenges
I assume that questions from ongoing math competitions are certainly off topic, and perhaps even deserving of their own off-topic close reason. But should we consider old math contest problems on topic? Say, is it OK to delve dig up a question from the IMO archives and ...
Proposal: Math Challenges
On Puzzling Stack Exchange, it's considered on-topic to post a puzzle as a question. On almost all other sites, something like that is off-topic and would be downvoted/closed.
Will it be considered on-topic to post puzzles and/or math challenges as questions?