I believe HIP-0002 should be expanded and an endpoint listing available addresses should be implemented.

For example, a GET request to https://<domain>/.well-known/wallets could retrieve a list of supported currencies.

The response could simply be a comma-separated plain-text list. The currencies could either be represented with their symbol, such as BTC,ETH,HNS, or with their SLIP-0044 coin type, such as 0,60,5353.

Other blockchain naming services have implemented similar features.