Hide Ticket Forms based on Customer Organisation

I'm aware there is an article on this issue but it is outdated for our theme version (Copenhagen 4.2.3). We have never changed our theme and this is the standard theme out of the box.

I was speaking to a Zendesk support agent on this issue who stated that the workflow I included in the link above will not work as our theme version requires React to hide the forms. 

What I am looking to achieve is the following; 

I have 3 ticket forms. Form A, Form C & Form F. Form A is the generic ticket form all our customers. Forms C & F are specific forms for 2 SLA customers we have. When customers log into their portal to raise tickets, we want the correct form to display based on that customer's organisation. 

It would be great if someone could help me on achieving this but I also think this should be a standard feature provided by Zendesk and I'm very surprised a feature like this does not exist as standard.