It was the first time I've seen a real grub2, not the transitional package 1.99. So it's not strange, it's simply real grub2 and I've to follow it to be up to date and allow coexistance. For the transitional package the installer is tested already. Give me a few days more to fix the "real grub 2" issue. Changing the grub-directory is not a good idea; if you look into Ubuntu it looks the same as in Jessie.
My own distro is based on "Wheezy" and the refractainstaller-yad (that is being tested on my bios-firmware based development computer) ported it succeccfully to uefi-firmware. The Wheezy-ISOs themselves will successfully install on uefi, if you choose the 64bit (amd64) versions. My uefi-notebook had Windows 8.1 preinstalled and after installing "debian-7.5.0-amd64-DVD-1.iso" a landed with a perfect dual-booting system.
So in the worst case install Windows 8.1, followed by Wheezy and you'll be ready.