Cludgey how?
Becuase this system requires more book keeping and much more margin for errors. Introducing up to 16 more dice rolls in the post game isn't a good solution IMO, not for something that doesn't seem to change things all that much. EXP just seems like a change for change's sake.
Just a few comments - if I leave something out then I am agreeing with your statement:
1) Rookie teams get ramped up to their first skill faster than the current system making it easier for them to be competitive in the league.
The net result is the same isn't it? It just means your team basically is almost never going to have inexperienced players, this seems a tad unrealistic to me. Some punk getting an MVP doesn't seem right either but is there really so much of a difference to warrant a change?
3) Getting a skill roll no longer has a possible penalty associated with it.
I think this system just shifts the timing away really. So what if you roll when you get a skill or when he picks his nose for the 12th time in a season. The fact it happens with the skill roll is a good way of streamlining the process.
5) The average player doesn't get his first permanent aging effect until his 22nd game.
This has been pretty much the effect I have noticed in our league anyways.
6) Maintains the coach's choice as to who retires and who stays (ie doesn't force retirement)
How so? Ageing hasn't forced retirement of an of my players. I can live with the odd niggler, and the AG decrease on my star (Norse) blitzer hasn't been an issue at all in about 8 games or so. Sure sometimes you get a crappy result, but them's the breaks! It seems rare enough to not be a problem.
7) Links Aging with the actual age of the player.
This is the biggest problem with ageing. The current system shouldn;t be called ageing, it should be called "wear and tear". The fact that it's called ageing is unfortuante and shouldn't have been called that in the first place. In my mind my team is playing pretty much in real time, the fact that a player gets a stat decrease or whatever because of the "ageing roll" makes way more sense if you thin of it as taking abuse through playing. In fact, in our league we call ageing "SPOOTEG" which translates roughly to: "Snot Pounded out of them Every Game".

Removes the old problem of freebooters and dead players stealing your MVP.
Yes this is a problem, but easily solved by adding a line to the MVP rule I would think. Perhaps MVP is not even the best term, maybe it should be called Experience!
10) Actually encourages player turnover of older teams (ie 20+ games) better than the current aging rules ... ie it steps them up a little as was desired by several reviews of older teams (20+ games) under the current LRB rules.
This is true to some extent, but since we use a system at the end of our season to level off highly developed teams (which this year will be teams like mine with TRs around 250). I think that ageing does a pretty good job of making you think twice about keeping aged players though. Although I have kept 2 of mine, my star catcher with a niggler has been teetering on Asstitant Coach status recently.
And for the cons...
In relation to the current aging system, Bash teams will age faster and Agility teams slower
I don't think this is an acceptable con. Any attrition system should affect all players equally.
Anyway those are my concerns and comments. I think if people stopped thinking of ageing as a player's actual age and thought of it as damage accumluated from playing a sport where people die on a weekly basis they wouldn;t have such a problem with it.