Great, thank you. I'm still new to this, so some of the acronyms are unfamiliar. I found a GHD, which looks like it has the quality you recommend.
I'm not sure what a step platform is, unless you mean something like this. But I don't see how that relates to saving space on weights.
I understand an ab roller to be this. I remember using one of these once and was impressed with how much it seemed to exercise my abs. Good suggestion.
As for suspension system, would that be something like this? Would a weight rack serve this purpose?