SAP integration (API) approach for third party brokered scenario

We have a mature SAP estate with S/4HANA (1709 on-premise) at the centre as our core ERP application. We have used SAP Process Integration (7.5) for many years for integration between SAP and non-SAP applications (A2A & B2B). We also have SAP Gateway (7.5) which we've used to leverage OData REST APIs to support Fiori apps. And there are older technologies still in use (e.g. BAPI/RFC, ABAP web services and file transfer to name a few).

Our latest project requirement is to integrate Microsoft Dynamics 365 with S/4HANA but we would like to use Talend as the Enterprise Service Bus (middleware) which acts as a data hub for our institution outside the SAP arena but we would like to extend it's use to cover this new scenario. There are likely to be a mix of real-time, near real-time and batch interfaces with a desire to use an asynchronous messaging pattern for queuing.

Talend has an SAP connector for BAPI connectivity and a REST connector which could be used to call OData services (exposed via SAP PI or Gateway).

The dilemma is regarding options for connecting to SAP via Talend:

• Option 1 BAPI (RFC) exposed via S/4HANA - this is an old proprietary integration method/protocol albeit quick to build. My concern with this option is future proofing our eventual move to S/4HANA public cloud and the likely deprecation of BAPI over time albeit this could be many years away by which time technology may have changed. Or perhaps the proprietary aspect can be overlooked as Talend is able to address openness of SAP data and BAPI is likely to be supported for many years to come?
• Option 2 OData REST APIs exposed via Gateway - these are intended for UX integration not A2A/B2B scenarios so this option doesn't appear viable.
• Option 3 OData REST APIs exposed via SAP PI - this would incur licensing cost for data usage and is not strategic (we have still to decide whether SAP Cloud Platform Integration, Talend or some other middleware may supersede our historical use of SAP Process Integration).
• Option 4 OData REST APIs exposed via SAP Cloud Platform Integration - we haven't licensed this and don't have the required skills

OData offers benefits over BAPI being an open standard (both for integration specification but also authentication) and with regards to flexibility (e.g. dynamic parameters to influence request/response).

I'd be interested in views on what approach/protocols community members would recommend given the dilemma presented? And are there other options to consider.

Thanks in advance for any contributions.