If it switches to ed25519 keys it can leverage Mainline DHT.  There are no DHTs that support secp256k1 key and if you bootstrap one, it will probably stay as small as the number of relays, because these are the entities willing to run infrastructure in the first place. 

 It doesnt need to switch.  Just each key signs the other one.  It's trivial, 10x easier than NIP-05.   

 yes but clients who don't know you by your pubky, will not see your cross signing unless they can resolve your nostr profile.

but maybe that is OK if it only needs to be done once. 

 The pubky is in the profile, so every client sees it.  It's way easier than NIP-05 which every client already does.