Take a look at the open source program Method5. (Disclaimer: I am the author of that program.)
It lets you run a SQL or PL/SQL against any number of databases simultaneously. All the work is done within Oracle so it works with SQL Developer or any other IDE.
Install it on one central management database and configure it to connect to your databases. (This may be easy or painful, depending on how many databases you have and how standardized the environment is.)
Then take any statement like this:
SQL> select * from dual;
D
-
X
And run it like this:
SQL> select * from table(m5('select * from dual'));
DATABASE_NAME D
-------------- -
db1 X
db2 X
db3 X
db4 X
....
A few caveats:
- Currently it only supports SQL and PL/SQL, not SQL*Plus scripts. But if your SQL*Plus scripts are just a few simple statements you can easily wrap them in a PL/SQL block.
- This program was built for DBAs to rapidly run statements against hundreds of databases. If you only have a handful of databases it might not be worth the trouble.
- The system is built on database links and you mentioned that database links are not allowed because of operational procedures. There's nothing inherently unsafe about database links and I think the only reason organizations ban them is because people often misuse them. I went to great lengths to ensure that Method5 does not repeat any of those same mistakes. It doesn't use shared passwords, it removes DES password hashes, etc. See the file security.md on the project page for more details. That information, as well as the program being "commercial off-the-shelf software", may be enough to help you make a security exception.