No, ESRT2 supports arrays > 2TB. The limitation is for physical drive capacity. I have 2TB disks, so I am able to configure 6TB RAID10. The issue is that I cannot install Windows.
I still don't understand how to use efi boot.
I have an idea to configure two arrays: 2TB RAID1 and 4TB RAID10 but it is not the best way I think.
Unfortunately ESRT2 doesn't support UEFI boot, which means you can't boot from a VD larger than 2TB. For RAID 10, only one VD can be defined for the entire array.
AXXRAKSW5 provides ESRT2 RAID 5 capability, and you can create two VDs for the same RAID 5 array. Otherwise the only solution is like you said, 2TB RAID 1 and 4TB RAID 10.
I have a similar problem, but with Linux. I have got a workaround.
This may be very unviable, but works: Use an USB drive to store the bootloader.
In almost any linux distribution, you can store grub and the /boot/efi folder wherever you want, including USB drives.
On Windows, you can try this: WiNToBootic - the ultimate Windows 7/8 USB Boot Disk Maker