Havesome/dunno:
Regarding individuals not continuing due to the cost, that is why it has so far being implemented by communities and not by the individuals.
As for unscruplous shadchanim, there will always be some abusers to a system, to date it hasn’t been a issue and anyone who takes advantage can always be disinvited from the project.
As for the two date minimum: Even getting to one date takes a load of work. If it’s not a absolute bomb the shadchan would receive 100 which is reasonable and thus we would have a army of people paying attention to the slightly older girls.