I have asked this on the gitter channel a while ago, but it seems it was never recorded anywhere.
EIP-615 had a static version of JUMPSUB, e.g. the destination is an immediate. This posed a problem, to which versioning was proposed, and ultimately led to the then-rejection of EIP-615.
EIP-2315 has a dynamic version of JUMPSUB, e.g. takes the destination from the stack.
I would like to see a static version of this in the future and hence asked to consider that here and design the proposal with that in mind (to be consistent), that is to have both the static and the dynamic version of JUMPSUB, but not implement the static version of the opcode now.
If subroutines are dynamic jump themselves how is disabling other kinds of dynamic jumps helping?