Is it possible to create intercompany transactions via suitescript?

advanced intercompany journals, yes. multibook journals yes, depends on what record type you're looking at

@Sciuridae54696d Paired Transactions PO & SO

via the inate special order functionality/ dropship-po also yes. But you'll need to assume additional development time for field mapping etc Otherwise it's still plausible, but it will be a full customization option