Skill level be damned. Get the motor you want and can afford.
I've never seen the skill police where I ride.
If I was into jetskis to develope skills, I MIGHT(but probably wouldn't) agree with the "little motor work on skills" theory. I ride because it's fun. More power is more fun. The only possible exception is in the surf when it's big and/or nasty.
You'll always get used to the power, even if it seems to much at the start. How many times have you ridden your freshly modded ski and thought "this thing rips". By the end of the season, you're wanting more.
Sure, you'll probably develop better skills trying to master tricks with an underpowered boat, but you're going to end up spending more for each build as you try to run a motor that matches your current levels.
Go big, ask Art what he thinks and then get him to do it....you can't go wrong. I went big, I'm crapping my dacks, but I know I made the right choice for the long term.
For some riders, sure, you can learn. For others, having too much power can really delay the learning curve.
I good 701 that has a nice port package, head, pipe, prop is perfect to learn rolls on. The power is very predictable. If you cannot roll or stab, hopping on a 785 cc Stroked Lamey with 49 Full Specs and MSD TL is not going to make you be able to roll any easier. More times than not you may end up swimming back to the ski because you could not hold on to it.
As your skill levels progress, bump up to a big bore setup. Go from there, when you hit the point that your motor is hindering your ability to advance your skill level that is when you bust out with the Baddest MF'ing engine package.
Case in point, Ratti, he started out on a stock SJ in 04. By 05/06 he was running a nice ported 701, as he got better he stepped up to a Big Bore, his tricks got better and bigger. He is not running an XScream Monster.
What if you don't care about progressing your skill levels, about barrel rolls, about perfecting your tricks according to your engine power?
I bet there's more people of that kind out there than what you describe.
(Good for the builders!)