I have seen some people posting here on this forum that own 10+6.
The 10-6 gap is certainly doable if you have some experience in riding both little and a lot of power.
I have a craveHL for the 6m (and a 10 A roam) and I don’t necessarily need a kite in between.
I weight about 75kg and I can ride the the 10m from a little over 8 knots (preferably 10+) up to 20 ish knots if needed.
The 6m is nice from about 14-15 knots and up to high twenties.
I did get an 8m but it’s a luxury rather then a requirement. I am riding on an often gusty lake so it’s a bit harder to properly size the kite without being partially under or over powered.