Well, you cut a section of boxed sheetmetal, and replace it some steel plate. Yeah, I know. Second, the WJ is extremely rigid as far as unibody goes. Couple that with a Clayton(additional subframe).. Solid.
Additionally, the only mounts forward of the motor mounts, are the steering box, and track bar.
Any flexing in the unibody will happen between the axles. Not at the extreme front. And, I would argue that the member they build(and those that have made such a plate on their own), is stronger than small section of boxed sheetmetal.
Regarding the additional protection, yeah, I get it, and I agree.
Either way... I like ARB stuff, and there are a lot of other options out there. Some I like, some I don't. I don't think you can really go wrong with any of the available choices.
Chase