Why not convert your existing zones over to UDMF and give its vastly enhanced way of level building a shot. So far, it has been enough to encourage some players to get into mapping and others who stopped mapping in the past to come back (according to the increasingly busy mapping channels on Discord).
The first iteration of Khronos Island for instance, would likely become far easier to make changes to, simply because of native sloping and multi-tagging. 2.2.11 also allows you to use the entire grid now because of fixes related to BSP building.
