When you craft T10 gear, prefix/suffix from t9 doesn't transfer to newly crafted t10. My suggestion is, that if your suffix is leveled up to max [lvl 10 atm] It's going to transfer to new gear.
Example: I have a T9 bow with power suffix and penta spread prefix. I level up my power imprint to max. When i use that bow to craft T10 bow it will have lvl 1 power suffix on it 100% guaranteed. Prefix won't transfer, cuz it's not leveled up [I can still add 5 prefix imprints to be 100% sure my weapon has prefix and suffix].
I think this is a perfect solution, cuz right now THERE IS NO POINT TO LEVEL UP your suffix, cuz t10 won't be the highest tier and it's a huge waste of materials to level up your suffix atm.
Btw to level up a suffix to level 10 isn't easy and it would be a perfect balance imho.