Is IOS254 the BootMii IOS? I ask because in earlier models, the IOS254 is not there, but in newer ones it is. I was wondering if I am correct. Also, if it is the BootMii IOS, could it be recoded, deleted, or otherwise changed to allow newer models to allow BootMii/Boot2? Just a curiosity.
Yes, IOS254 is currently where Bootmii/IOS gets installed to. It can be put on any model, you just probably don't see it on earlier models which have Bootmii/boot2 installed because there's no reason to have it. The answer to the latter is no. Earlier models have a vulnerability in the boot1 sector which allows for Bootmii to install in boot2. This was patched by N in models after or around the summer of '08 and no workaround exists.
"I think that the Wii is a beautiful piece of hardware, and a broken Wii is a tragedy. It doesn’t matter why or how." -- Bushing