SC as Euphonium Plugin?

[AxelJust]

Is it realistic to implement it as Euphonium Plugin?

[CarlosDerSeher]

I don't really know the internals of Euphonium so can't give a good answer here. It mostly depends on how much abstraction there is in the playback part. You really need close control of the i2s part.
Maybe a short example, if there is a ring buffer in Euphonium you push received samples in and the playback is handled elsewhere then no, it won't be possible easily.