The point that you cannot change a redemption booking and when cancelled only get back 50% of the miles is a clause / rule that will prevent lot's of people to continue crediting more miles than needed just for *G status. I find this highly restrictive rule quite silly and A3 should rather consider slapping a nice processing fee for themselves onto such transactions and allow changes before deprature as well as cancellation with full mileage refund.

Peoples' plans do change so to mee A3 miles are best used for short term notice trips where you are able to still find availability. Meaning I secure a trip using another FFP's miles where I can cancel against a fee and then try a few days before my now more certain departure to get the desired routing (not necessarily the same flight) using my A3 miles to avoid cancellation penalty. Given that in particular premium seats are sometimes released close to departure (within 2-7 days) this could work in a few cases, but make it a pain if you got large stacks of A3 miles that you want to burn.