Under the covers, all the SDKs (including PowerCLI) use the same calls, just wrap them for simplicity.
You'll have to parse your SOAP responses. You can get your target MoRefs from a lot of sources - RetrievePropertiesEx, SearchIndex.FindBy* calls, etc. Like I said, raw SOAP parsing against the vSphere API is painful. I just converted most of it into JSON for a simple Perl module (speed and memory optimization) and it was 2801 entity types and 615 operations 
You definitely can't integrate say PyVmomi or VIPerl into the toolset?