How about a catch-up mechanic for those of use who missed the first year + of fusions? Something like re-adding old champ fusions to list and creating mechanisms to get them. Something like 6 months after it goes live you can start doing first time fusion bosses again. For the shard bosses something like staggering in old shard infrequently within events that dont normally have shards (so you could earn like 10-20 shards a month on old shard fusions and get caught up over say a year).