Ok, so you go with your 81 sprinter on 64-76-87 train instead of 74-80-89 train, but complain about boring race?
Anyway, back to topic, there are really several possible solutions.
1.) Your solution, definitely an O.K. solution, if team formation can be done for 15min longer, but can already be done before. Problem: it would be a small disadvantage for those, who cannot be online in this 15min period vs. those who can be online.
2.) Show a team in the participant list if and only if they have all riders inscribed, so that no fake registration appears. Problem: People could still go out in the last second before the start.
3.) Don't show any participants at all before it starts, so that fake registration cannot irritate anybody. Problem: You don't know how many plan to participate, so you cannot avoid the too large / too small groups.
4.) Make a fair profit distribution independent from nr. of teams inscribed, so that nr. of teams becomes irrelevant and so fake registrations shouldn't influence others who worry about money.
5.) Ride for fun instead of ride for money.
Well, solution 4.) my favorite solution, but solution 5.) is more likely to be implemented in the game. Solutions 1.), 2.) or 3.) would be improvements perhaps, but not 100% sure and same as 4.) small likelihood that they are implemented by luques.