Portable Crafting Station
They already exist, you can get them in the form of consumables for guild commendations.
I couldn’t tell you if they worked in the HoTM (never tried it as I tend to get into a match in maybe five mins on a bad day), but they should be fine in WvW.
Maybe works in a dungeon, unless they fall into the restricted consumables list. Couldn’t see why they would though.