There are multiple RFCs with lists of HTTP verbs and axios only supports the more limited set, which for my particular legacy project meant I couldn't use any of the creative ones.
That really just sounds like an axios issue - I've built in support for custom verbs with nothing but plain-old ES5 javascript. The verb is nothing more than a string component of the HTTP request and it's pretty trivial to modify it to your liking (even outside of standard verbs!).