Instead of having a key being bound, is it be possible to change it to a general "use block"? I understand if it's not possible to change the mod for it, but would it be possible to get permission to change the revive function from a right click to a "use block" so my friends could revive me on a personal geyser server? Thank you.

Hardcore Revival already uses the Use Block key to initiate reviving. However, it's still something that needs to be initiated on the client-side, so assuming you're using Geyser to bridge Bedrock and Java, it won't work. Hardcore Revival is required to be available on all clients and server.