Though anyone may code a module for ULX doing so, the feature you request goes far beyond the simplicity (both maintenance-wise, and usage) of the true motto of the Ulysses "brand".
"Striving for Simplicity"
URS was created, and the original author actually included the same feature UnoLimited used.
Both original authors (me being one) simply have not had time (and in my case also, enough interest) to come by and update.
Garry included many variables within some of the entities themselves that would prevent usage of them.
I've not looked at Gm13, but presume they still exist, and perhaps, have been made better.