I've been thinking about it lately, and I was wondering creating a new item for the heroes to use.
The item would be a Heartstone and it would be buyable token at the shop (and why not even have it lootable from the dungeon floor like you would with a potion, on custom maps that is).
Hearthstones would take a potion slot in the heroes' inventory, and the heroes could buy them at 200 gold at the shop. A hero may carry only one Hearthstone at a time. A hero may use his Hearthstone at the beginning of his turn, and doing so uses up a half action (i.e. the hero may use a Hearthstone and attack once OR move his speed). When a hero uses a Hearthstone, the Hearthstone token is discarded and put back at the shop inventory. At the beginning of the next Overlord's turn, the hero is sent to town. A hero cannot use a glyph of transport and a Hearthstone on the same turn.
What do you think? I am quite unsure about details such as price, and how heroes would use them. Also I don't think I'd initially use Hearthstones in the 9 base quests — although if there was a way to make Hearthstones usable on these, that'd be great. Keep in mind that I only have vanilla Descent, so I have no idea how this item would fare in expansions (mainly Road to Legend and Sea of Blood , considering those expansions offer a different take on dungeons with smaller maps and such). Obviously, I'd print 5~6 Hearthstone tokens for the heroes to use.