Implications of gluing a panel made of hard and soft woods

This is actually a pretty common technique when making panels from smaller pieces, or it certainly was in the past.

As you have discovered, it makes for nice contrast.

Mechanically it is just as strong as any other panel you might make, allowing for careful jointing and glue-up. With today's excellent glues and correct clamping a panel like this is as good as a single-species panel.

My only caveat is that this technique was more common in the age before cheap sandpaper, and for good reason. Often such panels were planed after glue-up, and then maybe scraped smooth if finish planing wasn't possible (or you wanted the hand-scraped feel).

Unless care is taking with your sanding technique, powered sanders will tend to remove more of the softer woods, creating waves across the panel that correspond to the lighter and darker strips. This can create a situation where the woodworker ends up chasing level, removing way too much material in the process.

A longer sanding board with a light hand would have been the order of the day back then. Being very careful with even lighter orbital sanders would be advised. Or skip sanding except for the lightest pre-finishing, and in between coats of finish, letting the plane or scaper define level.