[ProtoDie]

Very well said.
That is a question posted often,,,,,,"I bought a frame,,now I need to figure out supension & steering"

Like you mentioned,,,there are a lot of frames built without having the suspension & steering figured out.

For those buying frames, maybe they can ask the manufacturer what rack & suspension they designed the rollcage for.
Ask for specific A arm mounting point locations

If they designed the roll cage with suspension, they should be able to provide this info.

It may not be realistic though,,,,,,,,,,,,,,,maybe just design & build from the wheels in.