Huzzah. I wrote a bit about the ambiguity of the triangle and why the fast > range > slow can emerge in a simple rule set, without adding resistance or special abilities.
The linked TVTropes page is a great example of the ambiguity in unit type matchups. There are just as many cases of speed beating ranged as speed beating slow.
I think the tiny example I wrote up is the most intuitive. If range is an advantage then a speedy counter mitigates that advantage while a slower counter exacerbates it. Not saying your solution isn’t also reasonable. I think as long as there’s a footmen ability before level 3 that heavily hints at an advantage over either footmen or knights then we’ll be in good shape.