Unfortunately it’s not quite that simple. Yes you can likely get AGESA but there is a whole bunch of other code you’d still have to write yourself and it’s not trivial without quite a few documents that AMD is unlikely to give you even with normal NDAs.
Now, Intel platforms you maybe have a shot at using EDK2 on, especially those with FSP. But Intel is unlikely to give you any support when something goes wrong and there’s probably no way to pay Intel to change that unless you’re a very big customer.