I've been contemplating using d6 in the place of d10s for the storyteller system.
The general consensus when brought up around storyteller player is 'just don't'. But I'm kind of stubborn so I'm exploring it.
So rather that 8+ on a d10 success is a 5+ on a d6. Which is somewhat close but not the same. Each step on a d6 is 16.67%. while a d10 is 10% each step.
The rules that this change effects the most is 10 again, 9 again, and 8 again.
10 again would have to go away, which I'm ok with. 9 again would be best to become 6 again also as, as making it 5 again would be too high an advantage. 8 again would be best to become 5 again.
I'm sure there will be times this fast and loose conversion will not work out perfectly. But I think for my liking it would work just fine.