- One work around is using MBOs. As already mentioned by Brenton, MBOs are getting deprecated.
- Other workaround is creating your own http services using Internet Communication Framework (ICF). NW Gateway also makes use of ICF, but using its own framework Gateway produces oData in these ICF services. (No additional licensing required for this).
- One more workaround is using SOAP services from ABAP (No additional licensing). But SOAP services are heavier than REST/oDATA and you loose binding functions of UI5 controls.
- One other workaround is using PI to expose http services. (You need PI license here).
May be you can tell why are you looking for alternatives so that you may get better answers,