So, I'm going to slightly disagree with my Head of Rules on this, in the idea that there's a safety or intention violation by creating this effect, because I believe that both Wards and Circles of Power are intended have the ability to create a prison-type situation (which I assume is what you're intending to do here), though usually to lesser effect than what such a combination would allow for. I also don't think the effect is ultimately all that powerful, either. You can already use a COP to barricade an entrance, so I'm not entirely sure what this setup is intended to protect against that can't already be protected via other means. I'm not sure how this situation would create an unsafe possibility; in fact, I'd argue that if there was enough space for cramped combat, that would be even more unsafe.
I will say, however, that if someone wanted to set this up, I'd make sure that the Circle adhered to size rules, because depending on the cabin, a LCOP might not actually be able to do this.
Edit: Because of the disagreement, I'm going to ask on the private Marshal forums, because it's entirely possible I didn't consider something.