In case of regular PRS tkt also, once you opt for upgrade the TTE marks your original berth as free and technically that can be allocated to next in line RAC pax or WL pax. Same can be followed in case of e-tkt. As the person requesting upgrade will be travelling in same train hence the TTE of upgraded coach say 2A class can always request his counterpart in lower class say 3A to mark the corresponding berth as free first then allocate new berth in higher class.
---
To be this logic...
more... of misuse doesn't seem to be a plausible option for refusing e-tkt upgrade if the case is so.