Does repurpose need to specify +1/+1 counter instead of any counter? In limited, it would be balanced around +1/+1s, but removing the restriction opens up the possibility of interesting deck building options in larger formats

I don't want it to work with -1/-1 counters. Period. I would rather have this only affect the most common type of counters for creatures than an interaction I'd rather never see happen. Also, in this continuity this would probably coexist in a standard set with a set with -1/-1 counters on it.