I've been looking at thermal printing mechanisms, particularly those that use waxed-transfer-to-paper i.e. older fax machines. The resolution isn't great but quite sufficient for most general pcb work. The only stumbling block is that the element used to provide the thermal transfer process won't accept a true flat paper (or pcb) pass through due to the 'bump' housing the heaters (presumably).
If the thermal print head manufacturers could make one that kept these 'lumps' out of the way then we're set to go!

Unless someone has come across a particular model that already has a 'flat' route through?