You're right here; your product is more flexible and suitable for almost anyone. But MDCU specializes on wise install order which advice full installation (98lite seems also not supported), so "preserving" (sp2.cab) and file-existance check is not need. As for MS article, i studied it when was creating inf scenario for RP. I noticed almost all flags not working properly with setupx installer (i don't know is it true), so i'm using setupapi (NT-like) installer, which is faster and correctly uses all flags.