would pro support be willing to help make this happen?
I don’t think so. Their policy (even in Pro) towards custom coding is, logically, rather limited.
The thing is that house cuts are being withheld by the house, not a payment service provider. Why would they put in a lot of additional administration to split payments, etc?
I am using Mollie, but Stripe does this too: for every payment made through them, they take a cut. Their pay-out is the revenue minus their cut.
So if you want a cut as well, you will need to take that out yourself – before paying your event owner(s).
This brings me back to your original question. You cannot have both! Either all payments go through your account so you can take a cut yourself OR you have nothing to do with the payments and pay-outs and use separate payment accounts.