Note that spring-webmvc does not depend on Struts itself; only spring-struts does. spring-webmvc just happens to include Tiles support, which in turn happens to be shipped as part of Struts. spring-webmvc essentially includes Spring's DispatcherServlet plus supporting classes (like for specific view technologies), just like spring-portlet includes Spring's DispatcherPortlet plus supporting classes. As a consequence, spring-webmvc has a lot of optional dependencies, which you can happily ignore unless you want to use the respective third-party technology.
Note that Spring's notion of web MVC is much more general than that of other frameworks. Spring builds on a generic dispatching infrastructure there, with HTML pages essentially being a specific use case only: The infrastructure itself is generic enough to handle for example the generation of binary reports as well as the generation of protocol responses. The latter is what happens in case of HTTP-based remoting: It's simply Spring's dispatching infrastructure used to expose HTTP request handlers that happen to process a specific remoting protocol.
Hence, I would argue that it is perfectly fine if you include spring-webmvc in your application, even if just for handling remoting protocols. Think about it as HTTP request dispatching infrastructure, which you use for processing a specific form of HTTP request. This is an intended use case that comes without any disadvantages, other than having a few further classes on the classpath.
That said, there is actually an alternative in Spring 2.0: You can use Spring's HttpRequestHandlerServlet; check out its javadoc. Since all of Spring's remoting protocol handlers are HttpRequestHandlers, you can simply define them in your main application context and export them through corresponding HttpRequestHandlerServlet definitions (with the servlet-name matching the target bean name) in your web.xml. This is another way of exposing an HTTP request handler, as alternative to using the DispatcherServlet. HttpRequestHandlerServlet is in spring-web, not in spring-webmvc, so has less dependencies.