Precisely because there's a lack of new users with good posts I believe that we don't need new merit sources.
How do you know we lack new users with good posts? I believe we had quite a lot new users who made their entrance in 2022-23, and ranked up pretty fast, as they were worth it. Shitposters, on the other hand, still find it difficult to rank up, as they should.
This is highly subjective.
To me, a forum where tens of thousands of people are active posting very regularly like in here, should also be having an influx of new users that are able to contribute that is akin to its active userbase. That would be at least a few hundreds of new users becoming legendary every year. If we check
https://bpip.org/Report?r=mostmerit there's only one legendary user in the top 1000 with a registration date of 2021 and 14 users from 2020. So in a little more than 3 years only 15 users reached the maximum rank. Also note that the bottom of the top 1000 have only a tiny bit merit above the required 1k to become legendary so I wouldn't guess that there's many more besides that.
I know this is an unorthodox way to check this but I can't find any better way to do so.