The concern I'd have here is that you'd end up with two totally different APs; a 2.4 GHz AP, on one side of the wall and a 5 GHz AP on the other. If your client mix is OK with this, that's fine. I'm thinking maybe you planned on splitting the pigtails from, say, an MA-ANT-25 across the two radios? On the face of it, that would give you one antenna for each radio, both inside and outside..? That really should be avoided; the recommended dual antenna chains connected to the same radio is what provides multiple spatial streams (for newer clients) and/or antenna diversity [to mitigate multi-path fade] (for older clients). These rely on both antennas having the same coverage area and the radio assumes that, in its operation. This is mentioned in the antenna installation guide.
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