For stuff like record keeping, where the reward pool would be irrelevant, I suspect a better approach would be to use custom_json because you can store arbitrary data.

The technical issue comes along when you want to retrieve the data. In that situation, you would store the data in another database. In which case, why put it on the blockchain at all? Well, you would do both. One to make it easier to retrieve (database) and one to verify (blockchain). Also, the blockchain version of the data would allow you to rebuild the database if something goes wrong.

One way to get both at the same time is to have a smart contract using a sidechain. It stores the data on the blockchain and stores an index to the data so there's no need to have an external database (because the sidechain is a database).

Unfortunately, running an entire sidechain for one app is usually overkill. So hopefully some day Steem Engine will allow arbitrary smart contracts for apps like this.