How would you do this? I made a really hoppy American amber a month ago and what I learned is that crystal malt doesn't really create sweetness per se, lowering the IBUs does. You can't just use a bunch of crystal or vienna/munich. Not only that, but dumping in those malts is going to make the beer too syrupy.
I suppose you could use a less attenuative yeast. But the human tongue can for sure taste the difference between a 70 IBU and a 100 IBU beer. 5-10 IBUs, sure, but 30 is going to be pretty apparent.
If I were a judge I would ding a 100 IBU American IPA for lack of balance. While I don't doubt that some people genuinely enjoy imbalanced bitter beers, they aren't in the majority.
An example would be I like to First Wort Hop all of my IPA's. On paper it increases the bitterness but to my palate, and others, it tastes less bitter because the bitterness is smoother. I know some people even calculate the FWH IBU addition as a 20 minute addition. Someone else was talking about Pliny or other well made Imperial IPA's.....on paper the IBU's are through the roof. I have had traditional IPA's that tastes much more bitter than Pliny though they are only 70 IBU's. A big part of that is ingredients...specifically what hops are you using and when they are used.