I think that's fair. I was able to make a script that let's you use either mousebutton, but when one is used the other is disabled for 1 second. This would allow you to swap on the fly, but would block double button mashing.
I think this would be a great middleground to make this a less painful speedrun, without giving an advantage over those playing the game without it.
Also, thats a crazy mouse. I think the existence of that should be enough to ban mousewheel rebinds.
I can post an AutoHotkey script under Resources that modify mouse inputs. But first a moderator should clarify what is legal for the speedrun.
Option 1: Ban third-party applications. Varies between people, but I am able to get around 6.5 CPS. Any other option would technically make it Tool-Assisted speedrun.
Option 2: Allow rebinding of right-click to work as left-click. This gives me about 10.5 CPS when mashing both buttons, but also allows you to alternate which finger you use for normal gameplay. This means every single action is still a button-click.
Option 3: Allow rebinding of scrollwheel to work as left-click. This gives me about 12.5 CPS. This is very powerful, as you are easily able to get 10 clicks in a single motion as opposed to having to do 10 unique clicks.
Option 4: Allow rebinding of right-click as a Turbo button. Probably bad, but allows moderators to decide on a CPS that is fair. Either that is 6 CPS so single-click still is faster, 10 CPS so it is easier to verify in runs, or something higher.
Are you using scrollwheel or a turbo function to click that fast? O.o