Gundam 00 Episode 04

[Yukimura]

Kraco are you on crack today or something? Visual guidance is not generally used for a good reason...it's extremely easy to fool. As to radar working, the first episode showed pretty clearly that radar would NOT pick up a Gundam (Exia was spotted visually by one of the people in the tower at the AEU base and the radar operator commented that his scope showed nothing). And in ep 04 the Exia was again picked up visually by some guy on the bridge and blew by faster than anyone on the bridge could even react.

And just because you can see something in the visual band doesn't mean it will appear on radar at all. Radio frequency EM radiation and visible frequency EM radiation are not the same and don't always behave same way in similar environments. The F-22 is plainly visible to the naked eye but has the radar cross section of a pigeon.

As to the ship armor. Gundam beam weapons have always been able to cut through metal like it was tissue paper. If Exia had started shooting at those ships with it's beam cannon the ships would probably have had enormous holes in them and immediately started to sink.