The BFTA rules already state that minimum distance is 9.1m and maximum 50.3m with kills of 13mm, 25mm and 38mm (min) to 45mm (max).
I know some FT shooters in the UK who already range in metres.
When shooting HFT, the same as field archery, I estimate in yards and really couldn't change to metres if I wanted to.
I have never shot a UKAHFT event, so don't know anything about the way those courses are laid.
"I'm your huckleberry, that's just my game"