Custom Properties in Properties Panel

Hi all.

I'm making a game as part of a small team, and I'm the only coder.  I am wondering if it is possible to create objects such as the player, platforms, pickups and enemies, and have it so that the other team members can just drag them from the library onto the stage and change properties such as their speed in the properties panel, without having to touch any code.

If anyone has any ideas on how to do this, it would be much appreciated.