I feel you. It really sucks that ASUS's recovery media doesn't let you replace or upgrade your memory or storage. Those are user-serviceable parts, IMO.

I am not sure if ASUS won't allow it by principle, but Eee PC 901 was using odd SSDs based on Mini PCIe with the same form-factor as mSATA SSD, but different electric circuitry, so regular mSATA drives couldn't work and you had to get an adapter converting mini PCIe into mSATA first. And once you plugged it in, primary master disappeared, so I guess that's what confused recovery media. They likely couldn't predict the future of SSD interfaces and were using some early prototypes before standardization.