//NJ, what is "the Prime Ministers gift"?//
Within his capabilities; something he's allowed to do; within his powers.
I accept that strictly speaking prorogation is only in the Monarch's gift, but it would not be exercised by the Monarch without a request from the PM.
I don't think there is any proposal to take this "gift" away from the PM/Monarch. What's proposed is the establishment of a Commission to look into whether any aspects of the UK's unwritten Constitution can be perhaps formalised.
Personally I think little or nothing will come of it (apart from a few fat fees for whichever of m'Learned Friends is chosen to head it up). They will produce a couple of amorphous reports which will lay in somebody's in tray for a couple of years, there will be another General Election and the entire matter, including the issue which initiated the farce, will have long been forgotten by then.