Good in theory but the NRL club supporters on the whole have no interest in anything else and won't turn up early to watch another game.
The supporters of Queensland Cup clubs love their football because it isn't played in a concrete stadium with overpriced entry, food and drinks.
If properly promoted so people would know about it many people would turn out for the early Qld Cup before Broncos games particularly those Broncos fans who also support Redcliffe and Wynnum.
I do agree with you about the suburban grounds being a better deal in many respects. Love the community easy-going feel at the QLD Cup grounds.