Hello, Strategist from Team 443 here.
Looking at the rules of the game this year, playing a defensive bot would be very difficult to put it lightly. Your maximum height restriction to start the match is 60in, and is also 60 inches if you are on your alliance station side, or the side they will be attempting to score at. However, when they come to score, they are allowed a maximum height of 84". In addition, you can't touch their robot in the key, or in their alley, or their bridge, which takes a significant amount of space, and their is also a rule on using more than one bot to stop the flow of the match. At most, defence will be played by bots who work as a defense bot who plays by the rules, just to slow them down, and also a feeder to carry missed balls to the other side of the field. If you intend to follow this path, know you're gonna need to know the rules forward, backwards, and sideways so you don't rack up big points for the other team.
Good luck with your decisions.