Ash would learn a great deal from this match-up.It could fit in with the plot actually since Shootie is arrogant and believes ash is a weak trainer.Paul would probably beat him without losing any pokemon and after the match he would tell Shootie how he use to be just like him(believed ashs training method was wrong and how he believed weak pokemon were useless for example Chimchar).Then Paul can tell Shootie how he lost to ash and that ash is potential to be the best.This will change how Shootie looks at ash by a small amount.
How about Ash proving his worth by himself? Isn't that his whole point? Isn't that why Ash strives to be stronger nowadays? To prove a point? To get his own point across, and not have his past rivals go to his present rivals and be all like: Yeah.. uhm.. He beat me although my pokemon were vastly superior, he's basically the second coming, so bend over already and let his ideology take you for a ride up yours...
In fact, I fail to see how this would work into Ash's rival arc plot, as it would severily make it come crumbling down like a brick house in front of an angry pack of Rhyperior/Tyranitar:
Shooti: I'm your rival, I don't like you, I don't think highly of you, I'll give this arc the tension it needs, ya heard!
Ash: LIKE HELL! I'm gonna make you eat those words like Paul!
Paul: Hey, Shooti, listen to Ash, he beat me like as if he was the second coming
Shooti: Then why should I listen to you?
Paul: Because I will battle you to show you that I'm good!
Shooti: But you lost to that country boy, who I just beat using the Vipélierre I just had for two minutes max, how fail can YOU be!
Paul: I.. I.. I.. ASH YOU IDIOT!!!
Ash: Hey what! Zekrom drained my mouse!
Shooti: There he goes with that idiotic excuse again
Paul: Well, he did knock out a Latios with that mouse...
Shooti: Holy crap, then my Vipélierre must be über! I'm sorry Ash, I guess you're okay by regular standards...
Ash: Crap.. Now I've got nothing to prove. Oh well, I guess I can still train these starters and bird I got recently and enter a league.. Just for kicks...
League time: Ash is totally unmotivated and loses in the first round: TOP128 NOOOOB!