Hey, I'm only about a year late responding to you, but I just saw this! Guess I need to come around the forums a bit more again. Making the players helmetless is a bit of a trick. I used the following method:
1. Find/create an unused colour in every single team pallet. It has to be in the same location for every team. That colour becomes your "hair colour". For this ROM I believe I used the skate colour, but I'm pretty sure I had a second spare colour as I also remember adding blood to injured players.
2. Using your favourite tile editing program, go in and draw over every single helmet with the new "hair colour". That's it! No more helmets!
You could also try opening my ROM with your tile editor and copy and pasting the helmet tiles into one of your ROMS. Might be a bit easier as the hair colour is unique on all my tiles so it would be isolated. Unfortunately I also drew over everyone's skates so you can't use my entire tileset without it looking like people are running on ice.
Hope this helps!