Yes, but please be cautious about this idea, it has many difficulties.
One important point : Coldstore users have to trust systems and technology more than other people. They are paranoid about security. How can you convince them that changing the way the private key works is going to be secure ? It is the fundamental point of Cryptocurrencies.
The integrity of the current private key system is guaranteed by not touching it.
Instead a second key has to be generated, which gives the right to use coin age. The next question in line is: "Can two private keys be distinguished?"
I think the integration of a second encryption algorithm may achieve this. It should allow for two private keys that are explicit distinguishable and assignable.
next question: "How to implement an account responding to two different keys?"
I guess it's some bitcoin and peercoin whitepaper reading....
You can solve this by creating a special transaction that will transfer the coin age from one address to the other.
This way you could mine with an empty address and have all your fund secured on a cold storage.
Of course the coin age should not be able to be moved from the second address, and the originating address can change the benefactor at any time.
However this will allow poll stake mining without needing to trust the pool with your money, which is not good for the coin because it would be too centralised.