Your sentence seems to be very polite and we have more polite way of saying it. However, your sentence sounds too polite and a bit cold, at least to me. I think using the normal polite way is better. If you use this types of polite sentence, you should keep using the same level of politeness for other sentences. If my friend asked for something with such a polite way, I would say "please don't talk with me such a polite way of speech." I'd like to recommend you to say: ( )さんと日本語の練習がしたいです。お願いできますか。 私の日本語の練習相手になってほしいです。お願いできますか。 Or a bit less polite: 日本語の練習相手になってもらえませんか / 日本語の練習相手になってください。お願いします。 It's only my oponion. I hope this was helpful.

I'm no expert, but that seems like a perfectly acceptable way to ask for assistance. As long as you use long forms I think you're safe.