in two minds about your under 19s idea nzfan - i instinctively hate favouritism without performance but club cricket pitches are terrible it's tricky to sort who is good and who is baaaad. however, i think compulsory under 19s would shut the door firmly on guys like wiggins, williams, mcewan, murdoch etc who are nowhere in age group nz sides but click in their early to mid twenties and establish themselves in provincial cricket.
you risk further devaluing club cricket and devaluing provincial cricket as a carry on from that.
australia have been consistently good for 100 years because their club cricket is excellent, no matter what the standard of state cricket looks like.
For a starter we are not as big as Australia or have as many vying for spots or our club cricket is strong enough to pick players from. At best our top grade club cricket is comparable to 3rd or 4th grade club cricket in Aussie. Auckland and Christchurch have reasonably good club level cricket. Outside of those two centers club cricket in the rest of the country is not top notch.
Since the last couple of decades owing to under 19s we have been able to get some players through who were raw but yet had the talent to go well at international level. Don't forget majority of the players in the national side now benefited by early selection to domestic sides straight from U19 national side not because they had great club record or outstanding performances at U19s but because they had the spark. Favoritism is the wrong word, it's early recognition of ability and talent. If you can play for national U19 side you can definitely play at domestic level. One or two players missing from club cricket makes no difference whatsoever. When I say compulsory selection for U19s I meant from national U19 sides. That's the least they can do. Otherwise the domestic sides will sign up near 30 year olds or guys that have had many chances but can't grab the opportunities.
Wellington had 4 U19 WC representatives in 2018, 1 in 2019. Out of them Ravindra has gone reasonably well, Bhula sparingly used, 3 others not even close and the last one we had Tashkoff the captain of the NZ U19 side can't find a place in Wellington A let alone domestic side. How hard is it to slot in one or two from this lot into the current side? Nope we have gone with Fraser Colson, Lauchie Johns, Johnson brothers, Younghusband and many more players picked from the club sides that can't perform despite so many hits. Clubs have likely played 4 out of 8 games right now on mostly artificial decks in Wellington.
Imagine having left Boult, Kane, Southee, Ish Sodhi, Jamieson, Munro, Young, Phillips, Ferguson, Rutherford, Sears, Nathan Smith, Duffy, Jimmy etc... to play club cricket for 2-3 years before getting them to play for domestic sides. Remember all these were the products of NZ U19s and got a domestic break as soon as they played for NZ U19s.