TianoCore has a small video shim that handles W7 INT 10h requeriments without needing SeaBIOS or anything else. Check here the Video Driver section about QemuVideoDxe: https://www.linux-kvm.org/downloads/lersek/ovmf-whitepaper-c770f8c.txt That is used by OVMF (TianoCore for Virtual Machines), thus Windows 7 works in pure UEFI VMs out-of-the-box without SeaBIOS as CSM or anything else.
I don't know whenever the video shim is used by default in TianoCore or not, but it should be able to get a Windows 7 in UEFI mode working. Some people even forked that shim to use in computers with pure UEFI Firmwares that doesn't have CSM, but you shouldn't need those. So I would begin by asking about whenever the shim is in current TianoCore payloads, and whenever you need to do something Windows side to migrate from UEFI with CSM to pure UEFI modes.