As far as I know, the lowest rank that got his merit source application accepted was Full Member, so it's not like you have to be Legendary member with thousands of merits earned to get accepted. But it makes sense that merit sources are usually higher ranks (Sr Member and up) as it mean you already shared quite a lot of merit and have some experience with it, and you had time to build forum reputation which is also important I think.
Thanks for the clarification and I agree with you that we are in new era I think theymos priorities is that Sr.Member up applying for Merit source got a chance to be accepted. Cause like you said the more you achieve high ranks you experience lot of things like giving Merit to those quality posters. But In my opinion rank doesn't matter even if you are in low rank atleast you helped those new users who've trying Thier best to post quality thread and reply.