Gotcha! Makes sense.
depends.. a lot of the time factor in implenenting it is just the risk factor (IE, integration testing and or finding that some solutions may just not work as advertised). So by risk I mean that, a lot of time may be spent going in a direction that wasn't going to work or could incur unknown integration debt.
https://habla.news/u/hodlbod@coracle.social/1741286140797
https://github.com/coracle-social/frith/blob/master/go.mod is the only relay implementation that already says it supports, but is on a now depricated version of khatru library.
Discussion
I wonder if a simple agent type thing (a bot with keys), separate from the relay itself would be able to do the nip29.. Things like this, should probably be investigated.. 🐳
I would likely try to either add the functionality to 1) strfry proxy, 2) a bot, or 3) integrate with a relay that provides nip29 and can run without locking up. (not necessarily in this order).