Bramlage does not have hockey arena dimensions. I can't think of a single arena built in the last 30 years with less floor space than Bramlage. It would be horrifically stupid to have an arena with less floor space.
Plenty of arenas have similar floor space, but bring the fans to the baselines via retractable bleachers. Mizzou Arena and Gallagher Iba were both built in the past 30 and AFH and Hilton Coliseum also have retractable bleachers. Ahearn had retractable bleachers behind the baskets, too.
I completely agree with you, the floor space isn't the issue its that we don't utilize that space. We shouldn't either. Without lowering the floor those would be awful seats that would only be used if the students moved to the baselines. The site lines there would be awful and would be empty more often than not. The flexibility of having that extra floor space is nice. Not sure why we don't use Bramlage for concerts and the such like we used to.
Also for the record when OSU renovated GIA the location of the seats in the lower bowl were not moved closer, they just put in new bleachers