Windows 7 refuses to install on gpt styled partitions in CMS boot mode

You've raised a number of issues, and more have come up in answers and comments....

Issue: Windows won't install to GPT on a BIOS/CSM/legacy boot

This is a Windows limitation. You'd need to ask somebody from Microsoft why they tie their partition table type (GPT vs. MBR) to their boot mode (EFI/UEFI vs. BIOS/CSM/legacy). Other OSes are capable of installing to GPT disks in BIOS mode. That said, such installations often cause problems. There are buggy EFIs that sometimes flake out with such configurations, or that require quirky details to be set in non-standard ways. Such problems are rare, but I'm sure if you sell as much software as Microsoft does, you'd never hear the end of it if you tried to support BIOS-mode booting from GPT disks.

As an aside, the acronym is CSM (Compatibility Support Module), not CMS.

Issue: Can't boot Windows 7 in EFI/UEFI mode

This problem was most likely a result of the poor EFI support in stock Windows 7 boot media. There are ways to overcome this, though, and a Web search should turn up lots of pages describing how to do it. The first hit I got was to this page, which is mostly about the installation process, but it includes a link to this other page that describes exactly how to create an EFI-bootable Windows 7 USB flash drive from a Windows disc.

Another possible cause of your problem was Secure Boot. Windows 8 was the first Windows version to support this feature, and the vast majority of desktop and laptop systems that ship with Windows 8 pre-installed have Secure Boot enabled. Thus, they won't boot Windows 7 installation discs unless you disable Secure Boot. Details of how to do this vary from one system to another, but it can be done via menus in the firmware setup utility, as described on this page of mine. I've seen reports of scary or confusing options, but the ones I've seem myself are relatively clear.

Issue: Replacing EFI/UEFI with BIOS

In theory, you can replace any computer's firmware. The trouble is that it's usually a lot of hassle. In a worst-case scenario, you might need to write the replacement firmware yourself, which is a non-trivial undertaking. As a practical matter, you might be able to do it by combining CoreBoot with a SeaBIOS payload. Even that, though, will require a pretty high "geek quotient" to implement, and will work only on hardware supported by CoreBoot. (For the record, I've never even tried this myself, so I can't offer further advice.)

For those who aren't uber-geeks, the only real option is to learn to live with EFI/UEFI. It's really not that bad, and it's actually got quite a few advantages over BIOS. It does have a significant learning curve, though. My own tips for success:

• Forget everything you ever knew about BIOS. EFI is different. Manufacturers try to make EFI look familiar, but that's like trying to make an orange taste like a banana.
• EFI is not BIOS. Manufacturers and many people use "BIOS" to refer to EFIs, but that just muddies the waters and makes people reluctant to follow the preceding piece of advice.
• Do not enable the CSM unless you know you need it and understand the consequences. The first thing the CSM does is to complicate the boot path, which makes debugging problems harder. Many people enable the CSM because of an initial hurdle getting an OS installer to boot, but in many cases it's better to overcome the boot problem in EFI mode than to enable the CSM. Sometimes it really is necessary to enable the CSM, but that should really be a last-resort approach unless you have good cause up front.
• Use virtualization rather than multi-booting. Multi-booting is difficult under both BIOS and EFI, and virtualization means that each OS can boot on its "own machine," thus simplifying the boot process.
• Read Adam Williamson's blog post on how EFI works. This is somewhat Linux-centric, but it covers EFI and how it differs from BIOS pretty well.

Issue: EFI/UEFI bugs

Yes, many EFIs are buggy. If you have that luxury, avoid most EFI-based computers sold until 2013-ish. Some, like Gigabyte's Hybrid EFI, which I write about here, should really be put out of our misery.

Sometimes EFI bugs can be overcome by updating your firmware. (Most manufacturers are guilty of posting them under a "BIOS updates" page on their Web sites.) Unfortunately, most manufacturers have given up on updating the most smelly of their old EFIs, so your best hope with some of them is to replace the hardware.