I don't see installing a couple of database access libraries as being a problem. libsybdb5, libxbase2.0-0 and libpqxx-3.0 aren't large and don't require installing the actual database server.
Splitting up kexi would have people install and run kexi then wonder why it wasn't connecting to their preferred database. Working out that you have to install another package isn't a great user experience.
I don't see installing a couple of database access libraries as being a problem. libsybdb5, libxbase2.0-0 and libpqxx-3.0 aren't large and don't require installing the actual database server.
Splitting up kexi would have people install and run kexi then wonder why it wasn't connecting to their preferred database. Working out that you have to install another package isn't a great user experience.