I dont believe the pipes are a standard size, so bulkheads wouldnt be an option, unfortunately. I havent looked at that portion in a long time, but I believe the pass throughs also threaded with plastic.
You would have to get in the overflow and remove the plastic part that covers the three holes. They are threaded to have the o.m.e. pipes installed. Then you could replace with bulkheads and add ASE pipe sizes vers metric. I had a leak so I messed with it underneath and saw that the plastic piece is silicone in from the top. Don’t see why it couldn’t be done. Even just getting up there with a dremel tool and remove the threaded section. Then making sure the bulkhead fits flush. Good luck and post pictures if you do this diy.