What you propose would work, but it's more complicated. I'm sorry, but I really don't see the point.
One of us is probably misunderstanding the other.
You keep seeming to say that when you pass coins from one block to another you have to adjust them for demurrage.
I think that creates complications that are not needed. Demurrage can be done just in the client, the blockchain does not need to do anything about it except to grdually increase the number of coins minted per block just enough to make up for the demurrage so that once the equilibrium amount of money is in circulation the slowly increasing number of coins minted per block keeps that number in circulation.
You basically only have to change the input and output display of numbers so that the same number in the blockchain displays as a lower and lower number over time and the numbers people type in as the actual at that moment value they want to talk about refers to a larger and larger number of blockchain-representation (epochal) coins as time goes by.
Basically if at the epoch I tell a client to send you 100, the blockchain representation will be 100. A year later though if I still say to send 100, of that day's coins, then on the blockchain it will show something more like 105 or so (100 * 1/0.95).
Similarly, if the genesis block mints 50 coins as represented in blockchain-notation (epochal coins) then when someone displays that amount in ten years or so it will be displayed as some 25 or thereabouts of that day coins.
The whole complication of changing the quantities as they go from one block to another just makes it all harder by not changing the values until they move. Since the values actually change whether they move or not it is best to have the demurrage - the change of value - take place constantly simply by having it happen in the display routines. At any time anyone can thus select a date as of which to display the values and look at any transactions or balances in the blockchain in terms of the actual value they did have, do have or will have at the specified point in time.
-MarkM-