Drafting tapered pants for better outer seam pattern matching?

If the fabric is not very stretchy, you'll probably get a bad fit and lots of creases in the hips and crotch area.

Sewing patterns are designed to best fit a 2-dimensional piece of fabric around a 3-dimensional human body. If you make major changes like that, you'll have to expect that the result doesn't fit the "standard" human body anymore.

My guess is that the pants would act like this:

They would only fit well as long as you spread your legs. While standing straight, you have too much fabric at the outside seam, especially at the hips. That fabric has nowhere to go, so it starts creasing and bunching up. Since there isn't enough fabric on the inside seam, it pulls and constricts uncomfortably, especially while walking or sitting down.

One possible solution is to taper the pattern on both seams and align the grain with the outer seam. Be aware that this can also cause creases and pulling. It's recommended to keep the grain line as straight down the leg as possible

Another alternative that works astonishingly well is cutting the pant legs on the bias. This was done for some historical clothing, mainy for the wealthy (because you waste a lot of fabric that way). Woven fabric has some stretch along the bias, so cutting pant legs on the bias allows the fabric to stretch over the knees and the bum when moving and sitting down. Of course this would lead to many intersecting stripes, which actually looks better than just a few intersecting stripes.