I don't see how this BIP is the same as J. Lopp's BIP. I also don't see any problem with the "Bitcoin Foundation" because for example Cobra-Bitcoin owns bitcoin.org and Matt Corallo owns "bitcoin.ninja" (while he is not a "ninja" he use that Bitcoin domain) this by no means makes him less trustworthy.

I see the domain https://bitcoin.foundation and it's BIP related subdomain https://quantum-resistant-bitcoin.bitcoin.foundation nothing more than another Bitcoin website. Probably when someone speaking like you are simply jealous. If bitcoin.foundation is not trustworthy than none of the bitcoin.tld's are. But this is just my opinion, you free to have other opinions on this matter. It's just not fair to claim that who owns such a domain is not trustworthy. Well, if I look at bitcoin.tld domains in any registrar I see that all domains that is in the format of bitcoin+tld are taken already. I don't understand how this would make all of them "not trustworthy". Again, this is just my opinion...

Regarding the signature size I actually found on the website https://quantum-resistant-bitcoin.bitcoin.foundation a very simple solution and that is called SegWit. SegWit can be used easily for this large signatures. Currently SegWit has a "block size" limit of 4,000,000 bytes and it can be increased as well with a soft fork to any size really.