That looks about right to me - not that I've even remotely thought of something like this before, but it strikes me as a good starting point.
You know, I was thinking...
RD asked a somewhat related question in his Granada "Pull the Pin and Count to Five" AAR when he decided to use a novel approach to the king-who-never-dies issue with some countries. He formed a "Grand Council" and I suggested that to spice things up he might want to consider modifying his "monarch" ratings slightly when he made DP adjustments (see
this post and the few leading up to and following it).
You might want to take similar sorts of things in mind...not modifying the monarch through DP adjustments, but perhaps using additional play modifiers based on your current DP settings.
Aristocracy
Since the game modifies the monarch's dip rating, so should you. High Arist should bump you up a notch, low Arist should bump you down a notch
Centralization
Thinking that this one might be a rounding effect. High Cent should have the effect of making a bad rating slightly worse and good rating slightly better (taking 4.5 as the middle ground). Low Centr should have an effect of offsetting both really good and really bad stats. Reasoning behind that is that a massively decentralized government might have a counter-balancing effect and and a massively centralized government would be toadying up to you completely.
Inventiveness
Not sure how I'd play this one...maybe no effect.
Mercantilism
I'd suggest that whatever the monarch's ratings, being low Merc (high free trade) ought to at least give you some bonus to placement and use of merchants, and that you might even consider applying a slight penaly to your "merchant" play if high Merc.
Offensive
High Off might make you more likely to get into strategically dangerous wars and to have a "let's go slaughter the enemy" approach to actually fighting them. It might also lead you to DOW by yourself when it wouldn't necessarily be such a great idea. Low Off might make you more likely to honour an alliance, and would tend to make you want to keep your guys at home and not press ahead too far into hostile territory.
Land
This would be a fun one. If you're strongly Land oriented then you get a bonus to your military and strategic activities during a war...but only for land forces. You would penalise your play with regards to naval affairs. The reverse would also be true. This means that a really crappy monarch would tend to have a little more of his campaign fought by the "powerful" side of the joint chiefs of staff, offsetting the monarch's deficiencies. A really good monarch would be hampered in some ways by them.
It should also affect your "war" decisions...are you more inclined to involve yourself in land or naval wars/conquest? Being strongly naval might also improve your sending out of merchants somewhat...
Quality
Maybe a monarch takes a little more care of his troops if they're high quality (offsetting some of the crappier monarchs' ratings) while being high quantity gives your monarch a kind of "devil may care" attitude? This would have an impact on your maint. decisions. This might also affect the way you approach attrition issues...high quality would reduce your incentive to pull an AI manouevre and throw 1,000,000 men in to siege a L1 fortress in a swamp for a year. High quantity and you'd be thinking "what do I care if they all starve to death? I can always get more."
Serfdom
High serfdom probably has no effect (?) but high Free Subjects might have an impact of offsetting (positively and negatively) a monarch's decisions when it comes to infrastructure.
Just some thoughts...you'd have to play around with them conceptually to see what you think. I'm really suggesting something more along the lines of a role-playing characteristic shift...
Oh...and don't forget to be a good boy and go suitably insane at the right times or avail yourself of a good minister every now and then.
The more I think about this (your whole game play approach) the more I think that I'm going to try this for the very next game I play. It sounds like a blast.
One final thought to put a smile on your face....
Imagine playing an 8-player MP game in Europe where everyone is subscribing to this approach.
For that matter, how about when only you are subscribing to this. LOL!
Edit: I meant to ask you one thing...just so I don't have to keep going and looking at your monarch files, could you include the monarch's ratings in the instalments too?