Would Steam/Age of Steam benefit from a non-constrained set of tiles
One step towards implementing a wider set of tiles, without adding pieces, would be to allow players to swap tiles on the board if it doesn't change their top face. In a small but significant fraction of situations, the tile you need exists as the unused bottom side of a tile already on the table. Within the rules, I have encountered at least one scenario in which the game outcome was changed by my being able to "waste" money upgrading an apparently random tile on the board just to recover the other side of that tile for the move I actually want/need to make.