Local building codes may not allow it.

Yep, check you local building codes first. A lot of places don't like that sort of build because they can be dangerous. Adding plastic sheets would be kind of tacky and also may not satisfy code.

I’m not sure if you realize it, but plexiglass scratches if you look at it wrong. Within 6 months the panels would look horrible.

Install the plexiglass and paint on wide black horizontal lines.

Where I live , this is allowed per code ..

Since that is allowed see suedonim75s note about plexiglass looking fairly awful in short order.

Makes sense .. since it’s only short term I could replace the glass sheets once in six months .. after kids are older , I wouldn’t need it..

Yes you wouldn't need it but when you go to sell, a smart parent would feel the same as you do now about young kids and you'll wind up limiting your market.

$1000 on the plexi does not seem like a wise investment to me to toss out in 6 months

Maybe my terminology was wrong.. I meant the glass sheets called banister guard you find on Amazon.. they are not very expensive .. (https://www.blueistyleblog.com/howtobabyproofhorizontalrailings/)

As far as your question on if it would be a problem when selling the home, it shouldn't IF it matches the style of your home. If, however, your home is not otherwise modern/industrial, this stair railing won't match in style and could cause an issue when selling.

Saw this on Instagram. Would look better then plexiglass.