Well here’s how I see it conceptually
We have the SafeCoin (SC) that buys certain amount of space (Allowance - A) and we have mechanisms to track the usage of A and its depletion (transfer of A–>Network) so what we need here is availability of A1–>A2 transfer.
The problem with this is that lowest denomination in this case would be 1MB I assume. But here’s where inflation actually comes to the rescue 
as SC progressively buys more space so does the A supply grows with it and I would add that in this case inflation incentivizes spending in very friendly way - you will be getting same amount of space for a lifetime but you wont be getting same value in network services…so once you’ve converted your SC to A you better spend today rather a year from now.