Well, these Frameworks are experimental, as stated above and one could say that they have a mind of their own- they choose their pilots rather than the pilots choosing them.

This is expressed by the following when someone enters one of these experimental Frameworks in an attempt to pilot them:

"We cast in the name of God... Ye are not Guilty." if you are the true Pilot, granting you the ability to pilot them with no repercussions. 

"We cast in the name of God... Ye are Guilty." if you are not the true Pilot and thus resulting in the Framework going berserk or trying to kill you.

"We cast in the name of God... Ye are not" if the Framework has questioned your path/ideals as the true pilot, and as a result will refuse to work for you until you can convince it somehow.

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Essentially, these Frameworks are relatively similar to those of the Megaduses of Big O and the Evas of Evangelion; they're somewhat sentient beings. They aren't blocky or anything of the such, in fact, they'd look more like something of a humanoid military-grade machine; they're more realistic looking than anything else. They can use normal weapons ranging from rifles, swords, and other various things, to adapting to use alien tech right on the spot... despite how dangerous as that might sound.

Some Frameworks may be bulkier or slender than others depending on their roles on the battlefield, but that can be up to the discretion of the players of course, however, there have been cases of slender models being Pointmen and taking the brute force while heavier models deal the damage.

In the end, they're humanoid looking and they serve mankind to save mankind... but if the pilot's will isn't strong enough, these special Frameworks will take control to do the job themselves.

I hope that answered your question, if not I'm really sorry. >_<