Upper_Krust
Legend
Hi Impeesa mate! 
Well don't be misleaded into thinking 'cosmic energy' just appears out of thin air; or indeed that overdeities specifically 'draw' cosmic energy. Such energy must already exist somewhere before it can be 'drawn'.
You don't get something from nothing.
Most overdeities are unconcerned with worship for a number of reasons; firstly most predated mortal races and by extension worship; secondly the amount of worshippers you would need to become an overgod (depending on your definition of an overgod) is billions going on to trillions so its all much of a muchness; thirdly they probably already had a substantial reserve of cosmic energy so gaining worshippers (which is not a rapid process) is not really on their agendas.
Divinity; whether from worshippers or not; is all measured in the same way.
So to answer your question my system supports all takes on divinity.

Impeesa said:Question: What support is there in the system for a being who goes from mortal to immortal (and continues to gain power) by drawing directly on cosmic energy as an overdeity does (without having worshippers)?
Well don't be misleaded into thinking 'cosmic energy' just appears out of thin air; or indeed that overdeities specifically 'draw' cosmic energy. Such energy must already exist somewhere before it can be 'drawn'.
You don't get something from nothing.
Most overdeities are unconcerned with worship for a number of reasons; firstly most predated mortal races and by extension worship; secondly the amount of worshippers you would need to become an overgod (depending on your definition of an overgod) is billions going on to trillions so its all much of a muchness; thirdly they probably already had a substantial reserve of cosmic energy so gaining worshippers (which is not a rapid process) is not really on their agendas.
Impeesa said:I thought of this specifically while trying to come up with a suitable analogue for the Planeswalkers in Magic: The Gathering, but it could cover a variety of other things as well (abominations who grow closer to their divine origins, things like that).
Divinity; whether from worshippers or not; is all measured in the same way.
So to answer your question my system supports all takes on divinity.