Remove both question and answer requirements
Meta is a great way for new users to ask questions about the site, so there shouldn't be a rep restriction keeping them from doing so.
New users should be able to use the Sandbox, so we should remove the answer requirement as well.
Rep requirements for meta participation make sense on other SE sites. Need help with something? Ask a question. Want to help somebody? Answer a question. There's not much else to it.
Things are a little more difficult here. Writing a good challenge or submitting a high-quality entry requires abiding a lot of rules. Meta PPCG is supposed to be the place for support questions, and brand new users are far more likely to need support than users that already earned some rep. Rather than having new users crash and burn on main, I'd prefer giving them the option of asking a meta question first.
Are there any downsides to removing the rep requirement? Probably. For example, before there was a Meta Stack Exchange, Meta Stack Overflow didn't have a rep requirement. 1 rep users that posted on Meta Stack Overflow quite often were question-banned on Stack Overflow itself and either wanted help with removing the ban or tried to circumvent it by simply posting their question elsewhere.
However, I don't think this will be an issue for our meta site. Question bans rarely happen on PPCG, and if they do, it's unlikely somebody would try to post his challenge on Meta PPCG instead. Also, not counting the Sandbox, Meta PPCG doesn't have a lot of activity, and moderators are immediately notified of new meta questions. Low-quality meta questions will get dealt with pretty quickly.
Posting answers on a meta site without having earned any rep wouldn't make sense on any other SE site. But we have a Sandbox, which is likely the most useful part of Meta PPCG for brand new users, and the very reason why we're even discussing the removal of the rep limit.
Are there downsides? Probably, but if it means granting first-time challenge writers access to the Sandbox, the advantages should outweigh the disadvantages.