I think a tag on transporting bikes is fine (which will almost totally be on car racks). As for a ski tag, I don't think its worth it. The questions are too niche and rare to merit their own tag (note that there's no coherence between the 3 questions which come up -- ski helmets for biking (should be under helmets or something), carrying skis on a bike (luggage/cargo would work for this) or taking a bike up a ski lift (I think thats the only question of the sort this site will see for years)).
The lift tag should also be removed since I don't think anyone will need it.
How about a "biking and" tag with a tag wiki entry along the lines of "Questions about combining biking with another activity – such as how do you carry your dog (or skis) on your bike? Please include the other activity in the subject of your question."