Here is a thought about finding a middle ground between the Maoist wish to declare a republic right away, and the rest of the political parties' (and international players') view that such a question should be decided democratically (and not by an appointed parliament):
During the constituent assembly election, hold a concurrent referendum on the future of the monarchy.
Each voter would answer two questions:
(1) Who are you voting for to represent you on the constituent assembly?
--- choice of names/symbols/parties
(2) Would you like a republic or a ceremonial monarchy?
The constituent assembly will then have to write a constitution around the winning answer of (2).
I see several advantages to this:
(1) It would decide the fate of the monarchy clearly, with finality, on one day, saving months of debate in the constituent assembly.
(2) The fate of the monarchy is decided directly by the people.
(3) The constituent assembly election goes ahead as scheduled.
Most likely the final outcome would not be different from either a parliamentary declaration, or long debates in the constituent assembly... but it would save time, keep the procedure democratic, and save the CA election.
If you agree, please spread the word. If you disagree, please debate here.
-Arnico.