Has anyone tried using other noodles?

It's worth pointing out that udon is available as a dry noodle product, shelf stable for long-term storage. That means you can purchase it from online retailers if it is not locally available and shove it into your pantry. It cooks up similarly to fettuccine; just follow the instructions on the package.

I think your dish will be great with the pasta you choose. I switch out noodles when i prepare Asian dishes quite often. For example I don’t particularly care for soba so I substitute udon because I prefer it. I buy them frozen & try to have them on hand because they are my favorite. On the other hand, we are more likely to have rice noodles in the house because they are dry. Use what you prefer. The only difference with most of them is the cooking time & method. If you get really curious & you have an Asian market, take a trip through their noodle Aisle and experiment. Good luck. I hope it turns out well, I think this recipe looks great.

Yes, fettuccine is an acceptable substitute.

In his book Japanese Home Cooking, famed Japanese chef Yoshihiro Murata (proprietor of Michelin 3-star kaiseki restaurant in Kyoto) specifically mentions fettuccine as a possible replacement in an udon recipe.

Note that this recipe isn't traditional, it's an "Asian fusion" concoction so it's even less critical to put udon in it.

Possible, but taste and texture will be different from original recipe.