I think I’d be tempted to try to fill the gap to make it original. Could be interesting to see what play is like with it open though.
I have a few machines in which posts were added in similar positions but then removed by previous owners.
I suppose my weird mod was when I had lots of extra leaf switches added to several switch stacks and lots of additional wiring from these switches in a bingo machine (United Manhattan) that was confusing as it seemed original but didn’t match what was in the schematics and manual (these are quite detailed!). The machine wasn’t operating properly and so I was suspicious that these switches were to blame. I asked about this in a bingo forum on pinside and had a suggestion from a bingo expert that all of this may have been added to make the machine legal in Ohio. The machine had a stamped license for Toledo, Ohio and so it was a great clue! I ultimately figured out what was added and then bypassed all the switches. The machine then worked as it should.