How to implement a Blockchain from scratch - adding system transactions

Adding a system transaction to a blockchain system is actually quite easy. Let we imagine the situation that we have something as a number of privileged accounts - they might be related to nodes as well and we want to initiate a transaction to adding a new one to these privileged accounts: 

- There must be a transaction that contain as an address one of the address of the privileged accounts. 

- There must be a state information in the blockchain containing the available set of system accounts 

- There must be a validation rule that not only validate the signature but checks as well if the related account is in the system state among the possible addresses. 

- There must be a state transforming rule, which in case the transaction is valid adds the new account to the state. 

The system can be started by adding to the first node a system right and then the first node can attach further nodes to the system account state. 

Optionally, there can be other special accounts or activities in the state that can be carried out only by system transactions. 

Certainly it is an open question if such a system is more vulnerable against forking attacks.

Such a system could provide the basis for realizing on-chain governance. Let we imagine the situation that difficult is a variable in the system state that can be modified only by system transactions. There might be one model that every authorized account can modify the variable, however we imagine that each transaction makes just a kind of a vote for the new value. If the number of positive votes reach a certain value, the new difficult will be considered in the future.