Blockchains generally are only about the "deltas" and not the entire blockchain, otherwise it would be impractical right from the get go. Every block only includes the differences. The problem is that these differences get thrown into a database that itself is growing far too large, so you can get by an example the new direction Vitalik from ethereum brings up is to split this out so you almost have subnetworks that are subordinates of the master. Of course, it is still early so we need to get more details. Now my main question is if Propthereum will have a secure database for the assets, and what kind of assets you are willing to manage?