Adga does mixfix pretty well. A variable in scope can indicate the places for arguments with underscores (e.g. _+_ or _=<_>_). The tradeoff for being able to use pretty much any symbol in identifiers along with mixfix is that you have use whitespace (3 + 5, not 3+5). Though I agree it doesn't scale.

You can use fluent interfaces to get past two args:

    myObject.doThing(a).toAthing(b)

Though that requires a good amount of boilerplate on the part of the library author.