> you would have to add schema attributes for every event property AND the logical aggregate properties.

In that case, you can serialize the hash-map with the fressian serializer (the one Datamic uses internally) and store it in an attribute of type :db.type/bytes. If the data is large (you didn't specify), then the link to an external data store is a good choice. The lack of an arbitrary shaped data type is a missing feature of Datomic, but is easy enough to work around.

I'm not sure Datomic is a mismatch. But, I don't know all the details of your situation. My main issue is with the lack of an explanation as to why you needed all those extra parts in the project page. The technical issues you solved, with those extra pieces, didn't come through in the project page.