What would you have used for generic arguments? I think they work fine, and make use of Func<T> often.

I haven't tried out many alternatives, but there's something about nested <> that seems to throw me off each time.

I wrote a library of monads for C# [1], and implementing the SelectMany method is a good example of how messy it can be:

    public static RWS<R, W, S, V> SelectMany<R, W, S, T, U, V>( this RWS<R, W, S, T> self, Func<T, RWS<R, W, S, U>> bind, Func<T, U, V> project)
    {
    }

I quite like F#'s alternative syntax for single type generics:

    Option<int>

Can be written:

    int option

Obviously it's a personal thing, so I doubt I would be able to suggest anything that would change your mind; I just had a quick go at an alternative, and I quite like this:

    public static SelectMany R W S T U V ( this self : RWS R W S T, bind : Func T (RWS R W S U), project : Func T U V) : RWS R W S V
    {
    }

    class Thing int
    {
    }

    class Thing T : BaseThing T
    {
    }

It's moot anyway really, it is what it is. I've just found it cognitively challenging over the years.

[1] https://github.com/louthy/csharp-monad