Someone else suggested this idea a few months back and I'd bump that thread, but I couldn't find it with my searches.

The basic idea was that knights who weren't leveling up any gear could have heat tanks (HTs) perhaps as an optional slot like a weapon slot (100e for 30 days), and these tanks would store heat that could then be deposited at the guild hall. Guild halls would take some very large amount of heat in order to be upgraded. The details of the upgrades don't matter too much, but lower levels could be something along the lines of adding something as simple as a wandering snipe. Higher levels might be something along the lines of a gate construction (you deposit minerals to make a gate like in the arcade, then it lasts for some set amount of time).

The idea here is to give knights a bit more incentive to keep delving into the clockworks after they've got all the gear that they want.