so regarding point 3, there is already a trash panel where you can restore every record which was deleted s.
In general we only execute soft deletes that means if you delete a record we only set a status to deleted and dont actual delete the record. This is also needed because of database constraints.
Updating connection names is not so easy since in Fusio there are multiple places where you reference such a connection name also at source code etc. so if it would be possible to rename a connection those code would break, because of this we have in general the policy that it is not possible to rename a connection. Instead we recommend to create a new connection and then you can also delete the old connection.
We have the same logic also for routes, changing a route has a huge impact of all your API users so it should be not easy possible to change a route. You can always create a new route and then deprecate an existing one.
Regarding customization, in general it would be possible to overwrite the connection or action service but in general I would recommend to stay with our implementation since this a core service of Fusio. Regarding point 1/2 do you need them while developing your API or do you have this use case also on an API in production?