(Main) Usage Case:

Player wants to make use of Blood Magic, which requires taking hits to their health bar (and on 1.10 requires a LOT of food to maintain natural regen).

Instead, they put down a pedestal + regen item next to their altar, which gives them a regen in a 2-3 block radius, and they can bootstrap things a bit faster....

So far all the items that work in pedestal also do similar stuff when just in hand.
So what item would this be for regen? And to give permanent regen I would think it should be very expensive.

An alternative in Reliquary is brewing potions which can give you pretty long regen so unless that item makes a lot of sense to get added I would consider potion the proper way to go.