I like it the way the Venetian Arsenal works currently, intentionally or not. Even with policies for building ships faster, it still takes a long time to make ships, and fighting over land generally has a higher priority than fighting over sea. Furthermore the Venetian Arsenal must be built along the coast and next to an Industrial Zone on the coastline, which limits that particular IZ from being able to radiate production to other cities.
If the disbanding exploit is the main concern, that should be the thing that gets fixed anyways. Only give gold for deleting Great Persons, and make deleting units give no gold at all or only very very little gold when they're deleted in home territory.