U19 Laws just encourages Coaches to select 8 loose forwards who can tackle for their engine room. The big strong slow oxen and bulldozers that are needed in proper rugby can be overlooked for the fancy boys that enjoy a good seagull and don't like putting their head into dark places.
HJ, IMO I'd suggest that even in 'proper rugby" the bullocks we used to see ponderously plodding around the park, leaving 6 inch deep craters that swallowed up unsuspecting hairdressers appear to be going the way of the dinosaur, particular at the elite level.
At school boy level I think it's great that lads who have the right physique and skill get the opportunity to build versatility into their repertoire rather than being type cast. I also think it's smart for the game long term because such versatility potentially keeps them playing in the game well beyond school.
I also don't know that the modern 15 man game can afford to have great big slow bookends on the park whose main contribution is just to the magnificent spectacle and test of masculinity that is "the scrum". Unless of course you are suggesting that we get rid of the 7 whining hairdressers and pitch three sets of tight five (apex predators) versus three sets of tight five in a scrumfest battle to the death. If that's what you are suggesting, I'd applaud you for your innovative thinking and reckon you are on to something!