I think this is definitely a highly viable strategy for this year's game.
Also, you can potentially address the portcullis by making the top of either the front or back of your robot wedge shaped (if you have enough space), sort of similar in concept to the wedges on Ri3D team REDACTED's robot (video here:
https://youtu.be/pOJLMLbW8DY, there might be a release video out later of their robot where you might get a better view of them). They pretty much work by fitting under the open gap of the portcullis and pushing it upwards as the robot drives forward.
Ideally, if you have enough space and confidence to do so, I would definitely go for the ability to scale the tower, since that definitely will be a trait that will set you apart from the other masses of breacher robots at competition.
If you think you can't make this goal, than make sure your drivers get plenty of time to get accustomed to driving with treads and crossing each defense, since experienced and practiced drivers will definitely give you an edge in competition, regardless if you have a climber or not.