Well, I don't want to force the title holder to accept any challenges, because there is always the possibility that the challenger will challenge with terms and conditions that makes them guaranteed to win. For example, if nobody else has challenged person A for the pack leader title, person B might make a challenge with the condition 'You have no equipment and I have a dozen dragons', and person A would be forced to accept.
Even if you make it so the title holder cannot decline symetric challenges, you still have the same problem. If person A has loads of sword skills, and person B and loads of spear skills, person B could make a challenge with the condition that they both use spears, and that match would heavily favor person B.
I don't want to get rid of special conditions for the title challenges altogether, because I want special conditions around the title nature to occur (e.g. wolves in the pack leader challenge).
How about this:
Anybody who is eligible for the title may challenge the holder. If the holder feels the challenge conditions are unfair, then they may appeal to me, in which case I will decide whether the challenge should be allowed or not.
The day before the start of each major tournament is the day of challenges. A title-holder must accept a valid challenge if one exists at the start of that day. They may accept challenges that take place on other days, but if there is a valid challenge for a fight on that day, then they must accept. If someone has multiple title challenges, for different titles or the same one, then they select one of those challenges to respond to. The other challenges are cancelled and must be re-issued for the next day of challenges if the challenger still wishes to challenge.