Many unofficial tournaments have already been held, and nothing happened; people participated.
If a person comes with the goal of participating in a tournament and testing their skills, then why not play in an unofficial one? Not everyone plays for overall dominance in Heroes; many play just for fun.
...wanted to create some kind of tournament, but there will be an insufficient number of participants in it because...
I fully support the Grail system! I think that all participants in different tournaments who "decided to test their skills" in them will not object to these rewards. There should always be an incentive, because interest in tournaments fades over time. A clear example: heroesportal has its own reward system, so the number of players in various tournaments does not decrease, but rather the opposite.
I also understand the Creator's reluctance to do this, because such implementation requires a very large, time-consuming job, which is difficult to carry out, at least due to lack of time. But surely there are no professional programmers on the entire forum who would not help with this? I think we can find willing people to help ;)