Solved.
It works with only two actions, NWA_READONLY and NWA_READONLY_ASJO.
Note that there are two NWA_READONLY available from actions repository, the one I needed was the one from application tc~monitoring~webservice~app.
After a lot of tries I decided to add all the actions beginning with string NWA_READONLY. There are nearly 140 of them.
This allowed the system overview panel to retrieve the data.
Then I was planning on eliminating actions one by one until it didn't work anymore.
Luckily for me, I ordered the actions alphabetically and found the one I needed on the second try.