I don't see how this would happen, when Namor was able to keep from being destroyed by the Sentry, fought Hercules without being crushed, and many other feats. Captain Britain is a powerhouse as well.
Captain Marvel was amplified by every mystic this side of Santa Clause. Captain Britain was also once amplified by every Captain Britain in every divergent reality, but I don't think that he is the Captain Britain that we are discussing here.
But he was still getting ripped, and still lost with an amp.
Not sure if the lightning would work on Namor, as he is immune to electricity. This is just a guess on your part. It could work, but since we have never seen Marvel shock Namor, he may be immune to it. Whereas Gladiator's laser vision would turn him into a wet noodle.
At the same time we can't really say how much power the Spectre was exerting against Marvel, the only thing that we do know, is that even after Marvel was super amped, he still lost. So logically when he had no amp he was less than he was with a major amp. Just think about it for a moment.
Even considering that Namor has hung with guys in that class on several occasions? Pitching Cap Britain in seals the deal IMO. This is Namor, not Aquaman, and in terms of strength, Namor is up there, and always has been.
Yes he is but he is still a notch or two or three below these guy's levels of strength.
He can hang. Captain Britain is the same way
CapT Marvel is stronger than both of them, is faster, more durable, and has his magical lightning attacks.
The duo could make a fight of it but I think this is an instance where they are both clearly outmatched to the point is makes a considerable difference.