Such a simple and obvious problem lies at the heart of this, and one which hardly anyone remarked on when Marshall converted:
It's simply far harder to convert when older and the body is way past its peak, motivation and commitment lower, and learning ability lesser.
Even a cursory look at successful NRL converts will show that the most successful moved youngest: Folau, SBW, Tuqiri in their early twenties, most of the failures and partial successes in their late twenties (in face the success rate of under-25s is very high).
But NRL players often prefer to have a full NRL career first, and play rugby as a kind of afterthought, a second choice, a final payday, often when contract negotiations fall apart.
It's also a mistake to buy these players up on the part of rugby.
A message should be broadcast to the rooftops that plays will not be accepted beyond the maximum age of 25 (earlier, preferably). Anything else is a speculative investment in a diminishing product: of course some players may succeed, but it is far more of a gamble, and with fewer years ahead to provide returns.
But there is one point where Kirwan made a bad mistake: playing Marshall sporadically. This is where Chieka understood his responsibility better.
A league player will make mistakes, be a liability and even a bad performer for many games before they have adjusted and so must simply be played every minute of every game to do this as quickly as possible. It's no good hoping they will get the game time necessary in cameos off the bench. Chieka started Folau in every minute of every game. Kirwan was terrified of Marshall playing damaging his team, and didn't realise that with an NRL convert the tradeoff is that they may lose games for the first half of the season, but in the second half may win them and for several seasons after that. But they need big blocks of games in order to learn the new game.
So the conclusion is that NRL converts can be a success, but aren't generally worth pursuing over the age of 25, indeed the younger the better, and that if one is acquired they must be played every minute of every game at least for the first season.
I don't believe Todd Blackadder's coaching does anyone any good, including Dagg.
Then again the other hopeful Andre Taylor is receiving less than wonderful coaching at the Hurricanes too with similarly negative results.
Old Bugger Retallick and Luatua are undoubtedly very good players, no doubt, and they are both young although more so Luatua.
But neither has yet suggested the impact of the two players that they're aiming to replace.
My point about Vito is that although he hasn't been that great, he HAS at times shown the kind of impact required.
Messam is a very high quality rugby player, and if Reid was gigantic, he would compliment him well. But while Reid may be the most excellent player, he does not have so much physicality that the 6 in the team can lack it. Messam is good against some teams more than others, but a more impactful player may be needed.
I see your point about some of these players being young and agree, while there is also room for improvement. But on the other hand some of the older players in the pack may get worse, even by 5 or 10%. Overall it will make a difference.
That outmuscling in the first half against England was quite striking, and if the improvement doesn't happen of the current players something different may be required.