There isn't really a need to handle each bit of HP gained separately, all you need is to count how many classes of each have a particular dice count. take that information bring it over stripping out the CON bonus which can be done even without api on the client end. As for the other sections, BAB, saves etc, you run into some other issues, but the largest issue isn't with the character statistics but with static text based fields. What do you do with them? Personally, I would strip them out and have it converted to an HTML and stick it in the GM notes, but other people might want to auto populate spell like ability fields from them. Again cumbersome, I don't have anywhere near the javascript knowledge for the roll20.. it is VERY different from web based. In theory you should be able to use the XML just like you use the eval scripts, and you can easily use those to check for tags and tell the system if it is. Listed as a Spell-like, Supernatural or extrodiary then assign it to Field X. But then you need a way of keeping track of how many class levels vs hit dice for DCs, and it rapidly devolves into a cluster. I hope someone does it, and I'd be more than willing to help match a character sheet to it (3.5 Only, I don't know the rules well enough for the other systems to try them).