Okay. Think about it. Isn't that the intent of the game ?....to disrupt your opponents harmony ?
Promoting to....A PAWN ? Can it Help ?

I cannot find a condition where promoting to a pawn would actually help a player.
I don't think it is legal in standard chess; you must promote to knight,rook,bishop, or queen according to the rules.
However, who says you can't make up your own rules?
I used to think you must promote to a captured chessman (or leave it as a pawn until something of yours is captured); OTB wiithout extra chessmen seems intuitive. It made the game just a sfun (playing with different rules).

Steinitz proposed it over 150 years ago with the intent of stalemate. It servers no other purpose than that.

I fail to understand how the position would even change if a pawn was promoted to a pawn. If anything, tempo would be lost. But I did not check the original message. So I will do so.

And if a piece some how demoted into a pawn, that would be a disadvantage unless that pawn can directly give the player an advantage to the position. Also if the pawn makes it to the eithgh rank and stays/promotes to a pawn, will it be allowed to move back, because unless otherwise indicated, the rules are that pawns move foreward and not backwards.

demoted ?....it stays the same.
Making it too complicated. It just stays a pawn & that's it. It becomes permanently dormant.

that would waste a move right? You get it to the eighth rank and then you have to spend another move just to promote it

If you promote to a pawn and it stays there, it would disrupt the harmony in your opponent's position. For example rooks on the eight rank wouldn't be connected anymore unless that promoted pawn is not protected by one of your pieces.
Just promote to a queen and it disturbs opponents pieces if protects like if you promote to pawn...
I wanna have AlphaZero wired for non-promo pawn chess in a number of positions to see if it can be beneficial.