In order to submit sites for UNESCO WHS status Taiwan would have to accede to the World Heritage Convention - not all countries acceding are members of the UN nor even of UNESCO but if they are not they have to be "invited" by the general conference of UNESCO - and there would seem no way in the foreseeable future that China is going to allow that surely!
See this earlier discussion in this Forumhttp://www.worldheritagesite.org/forums/index.php?action=vthread&forum=4&topic=257
You will note that "Territories or groups of territories that are not responsible for the conduct of their international relations may be admitted as Associate Members." - Can you see Taiwan accepting that? China might even agree if it did!!
You will get a few web hits for a search on Taiwan and "World Heritage site" showing what Taiwan has been doing
This one from 2003 identifies the following 4 sites as the most significant of 11 possibles (1 less than your 12 but they also suggested another site which should be looked at!) - Taroko Gorge, Mount Ali, the Peinan Culture Site, and Chilan Forest.http://taiwanreview.nat.gov.tw/ct.asp?xItem=840&CtNode=119
and this one has a list/description of 7 possible sites visited by an Australian "delegation" which had intended visiting 11.http://www.ausheritage.org.au/projects/bruce-pettman-undertakes-world-heritage-missio n-to-taiwan/
It seems perfectly natural and proper for Taiwan to want to be part of the heritage world. It has as much to offer and preserve as many other countries but activities concerned with actually going for WHS status would seem to be pipe dreams. It is somewhat illogical for UNESCO to fail to act to help preserve locations which might be of value to Mankind in general just because if "politics" - but logic and organisations like UNESCO don't always go hand in hand! I guess Taiwan could at least go through the motions of preparing and managing selected sites to WHS standards (and surely China DRC should be equally proud of such sites in Taiwan and ought to take a long term view to avoid making such preservation difficult). But I doubt that ICOMOS/IUCN, who evaluate potential WHS sites on behalf of UNESCO, would get involved in "evaluating" them as if they were being put forward for WHS status - though that is an interesting possibility! ICOMOS for instance is "is an international non-governmental organization of professionals, dedicated to the conservation of the world's historic monuments and sites." Since its role assisting UNESCO is only one means by which it achieves its objectives it ought to be prepared to help carry out its mission in other ways in Taiwan - indeed I understand that it does "deal with" Taiwan (??). But it is one thing to help preservation etc and another matter all together to get involved in "assessing" a site a la UNESCO - I doubt that it would! And IUCN is equally "non political" and, I believe, does work in Taiwan re natural conservation (whales/birds etc??) but the same limitation as to what it would be prepared to do if there were any hint of trying to piggy back on the WHS scheme would surely apply?
Of course there are other UNESCO lists such as for "intangible heritage" which Taiwan could also think of pursuing, but no doubt with the same result. For instance Taiwan possesses particularly strong "aboriginal" cultures possessing cultural activities which could benefit from preservation - but again unfortunately it would seem that recognition and support of such preservation is not going to be assisted by any official UNESCO recognition! The "World Biosphere Reserve" scheme is another UNESCO controlled one. The "RAMSAR Wetlands" Convention secretariat may be "hosted" by IUCN but has a membership restricted as follows "Any member of the United Nations or of one of the Specialized Agencies or of the International Atomic Energy Agency or Party to the Statute of the International Court of Justice" -so no room for Taiwan there either! No doubt there are some international organisations with which Taiwan could operate - just as long as they don't require international recognition as a sovereign state!