The database is meant for technical analysis. Things not relevant to technical analysis are not supposed to be there.
Database layout very likely won't change. Even Aux1 and aux2 are unused by 90% of users. The design addresses largest user base not outliers.
Right now there are 8 data fields plus datetime
Need more - You can use extra ticker.
Up to 16 can be stored if you just use one extra symbol per normal symbol. This covers 99% of usage scenarios.
Increasing the number of aux fields would greatly increase RAM consumption and that is big no-no.
Current design is the right balance of all factors, read this: