Span elements - no, pandoc doesn't support arbitary spans (there has been some discussion on the mailing list regarding options to implement custom spans, but the general consensus was no as I recall).
List items - again no, but you could potentially script a filter to do this - The pandoc documention has an example on adding an id* to links here, although you do need to code for every target language you are going to use
*in this case it uses the id to treat stuff as ruby, but there is nothing to stop you just sticking the id into the output as you need.