I'm pretty sure most plugins can be converted from ReAPI to fakemeta/engine. The only issue I see is when orpheu is needed, but signatures are already available in this forum for a lot of functions so the only thing left is to use orpheu natives like you could with any other native.
I understand this is not ideal, but I don't know many people here who actively use ReHLDS and could help you find the issue and fix it. That's why I said your best bet is to ask the maintainers of ReHLDS directly.