this idea is very simple realy, "Flexability" shards could be both prefix and sufix and could fit into item as either of them, they are available at very high lvl crafting and ONLY on bound crafting so this extra "Flexability" would be a very good reward for getting that high in crafting.
i know there could be a problem with "fitting" the shard in the "right" slot (prefix or sufix) so maybe crafting devices could gain new 3 buttons (show all, prefix, sufix) that would filter only the effects based on them, and could double as a way of choosing the right slot for "Flexable" shard.
i mean all new random generated items dont have any rules at all when it comes to prefixes or sufixes as they can have 2x prefix or 2x sufix on them with no problem.