Transactions creation is easy but reading is not. We need a financial parser that does that first formatting the data before creating the transactions and then reading it from the blockchain.
Eg: When a transaction of loan is getting created there is going to be several smart contract getting executed, this data needs to be stored in a chained order so that when ever we pull up say fetchLoan(1) we should have all the contract data with links to accounts and other services data if thats on blockchain.
Check Ortelius API , we can build something over the top.
Creating transaction per service level, that means indexer needs to know which service posting what?
Reading transactions chained from different chains , external chains or other chains or grouping them together.