Right now this framework could generate controller methods such as:

testControllerMethod( param1: string, param2: number, queryParams: { param3?: string; param4: number; }, data: entityDTO  ): RestResponse<SomeData> ;

This means that the method interface is a simple wrapper around http controller which doesn't provide any abstraction over http controller.
The user who uses such methods should be aware of where parameters should go (it is a request parameter? is it a path variable? is it an entity data?).
I would suggest adding a feature flag which provides a service abstraction layer instead of a simple HttpClient wrapper.
Maybe something like: serviceLayerInsteadOfWrapperLayer: boolean.
I think (not sure yet), that we could relay on null value of an argument as an indicator for a value to not being provided to the HttpClient.
So, maybe, we could generate an implementation like the next one:

testServiceMethod( param1: string, param2: number, param3?: string, param4: number, param5: entityDTO ): RestResponse<SomeData> 
{

  queryParams = {};
  
  if(param3 != null){
    queryParams["param3"] = param3;
  }
  queryParams["param4"] = param4;

  return this.httpClient.request({ method: "POST", url: uriEncoding`some/path/${param1}/${param2}`, queryParams: queryParams, data: param5 });
}