Hope it is OK if I point to my OpenNTF project soapgateQ!, which does provide a native Domino API with RESTful and SOAP services. No Designer or design changes are involved. Just place the database on the server and configure access control down to the field level. It works even in a DMZ scenario where the database source can't be made accessible to the web.
https://soapgateq.openntf.org
http://flexdomino.blogspot.com.mt