The disadvantage is, Reddit and other platforms will never add support for [fediverse hyperlink](fediverse://example.com/post/1337) Markdown syntax, or even start blocking it (they can already block known Fediverse domains but there would be backlash if they did).

Changing the scheme doesn’t really make any difference if it’s still just HTTP underneath. The scheme is just for indicating a protocol. So what’s the different protocol you’d actually propose?

Absolutely not. It should run on HTTP, as a website. Unless you want to build a client which would be somehow fundamentally different from a web browser somehow (note: Lagrange and Gopher Browser are just browsers), which would somehow be able to display data from every use of ActivityPub / “the fediverse” in a different context from a web browser, then no. What we need to build is website software more in line with kbin / mbin, collecting together all the different information of the fediverse into one interface.