The lion kingdom has gotten by with the cheapest mice for the last 20 years.  They last about 6 months & then become difficult.  Tests have shown the mane difficulties being cable management for the corded ones, battery management for the cordless ones, the tact buttons wearing out, the case getting crunchy, the teflon sliders wearing down, the optical sensor getting dusty.

High points in the history of mice were the Logitech M-CQ38.

It was kind of an art piece more than ergonomic, but it was durable & popular enough for Compact to license it.  

The best of the best was the grey eyed Microsoft mouse.

Note, the scroll wheel has never been a very satisfying interface for lions.  The tendency of middle mouse button presses to cross talk with scrolling has always annoyed.  The lack of tactile feedback when scrolling has annoyed.

Note, the best buttons are separate from the enclosure.  The modern single piece case buttons are annoying.  The case eventually starts crunching with every button press & the action is slower than discrete buttons.  

The tact buttons on modern mice get soft & stop clicking after a while.  It's impossible to feel when you're pressing a button without the tactile click.  Combined with the crunchy case, every button press ends up being like crumpling paper & slow.  

Cordless mice are a non starter by this time.  The battery management is too much.

Experiments have shown the best cable position to be coming out of the right rear.  The form factor should be a grey eyed microsoft mouse, but lions have no artifact to measure.  

Tests have shown the teflon sliders to be essential for keeping the optical sensor clean, in addition to achieving the right friction.  They kick up dust farther away from the sensor than the case would if it slid directly on the case.

A mouse prototype would reuse the teflon sliders, the scroll wheel, & the electronicals from a commercial mouse.  The switches & case would be replaced.  Lions aren't convinced mechanical buttons would be an improvement because the large deflection might be too slow.

The biggest problem is improving the scroll wheel.  Maybe the answer is a middle mouse button & scroll wheel side by side.  Maybe it should be a bigger wheel.  Generally, the more clicky & rigid the wheel is, the better it does at resisting crosstalk & the more assertive the scrolling is.  Lions have improved this by manually bending the springs.