The Share client interacts with the Alfresco repository entirely by means of the WebScript REST API. So if you wish to leverage the functionality that Share provides then you can either customize Share to hide the parts that you don't actually want or your could write your own client and the choice of how your interact with the Alfresco repository is entirely up to you, be it REST API, CMIS, etc. If you just want to display certain parts of Share in an iFrame then you'll still need to hid the parts you don't want - alternatively there is also the portlet option as was suggested on your other thread.
My personal recommendation would be to add the additional functionality (pages, components, etc) you require into Share using the Surf/WebScript framework and re-use the parts of Alfresco that you want to keep. However, you should be aware that such an extreme customization of Share would probably be quite a challenging exercise. Whilst WebScript and Surf may not be familiar to you they are the most likely to yield the best results as this is what Share is developed using.
Regards,
Dave