Cerebro, the original, had two major problems.
One, it used stairs to get to the main level, which was no longer practical. And two, it didn't exist, having been pulverized in the attack on the CIA compound.
Cerebro version two was sparse and sleek and elegant. The entrance was at the same level of the middle of the sphere, so the outside corridor led to the walkway led to the center platform without so much as a threshold to mar the lines. The walkway, no wider than necessary, had lighting along the edges so any visitor could see where it ended. The center platform, a circle dwarfed by the size of Cerebro itself, had similar lighting.
It was awe-inspiring, and spartan, and very clean.
"I like it," Charles said.
A week later, in his usual insomniac habit of trawling through Cerebro-space in search of a) Erik, b) any budding new mutants that might be interested in the school, or c) Erik, Charles actually found the one mind he was most desperate to find.
"Yes!" he shouted, and thrust his arms into the air excitedly.
He spun the chair around, zoomed towards the walkway, and discovered two things.
One, a two-inched raised rim was not enough to stop a determined wheelchair, or, for that matter, one that was moving at any speed.
Two, it was a very long way down.
"Ow," Charles managed weakly.
Cerebro version two point five was modified in the following ways:
Firstly, the walkway was wider.
Secondly, there were safety rails.
Thirdly, in case all else failed, a safety net about two feet down.
With sensors, linked to a console in the main part of the mansion, so that other people would know when someone fell off.
"It looks ridiculous," Charles complained, but secretly he was a little bit relieved.