All the Seed models I have (less Rouge) are all HG kits. Yes I know it does not have any grades on the box but it's widely accepted as HG grades in the shops where I bought them. So, the no grade 100 models you mention are the HG 1/100 grades I said.

I thought of doing what you said for Rouge, but like what I said it was really cheap when I saw it and I was attracted by the base, that's why I bought it. Would have loved to get the MG Freedom but I've already got the HG versions way before the MG was announced. I've got friends who still refuse to buy Justice Gundam because they are hoping for the MG version to be released.