Advice on how to setup my systems (xen, gpu passthrough, X)

Question

Hello Archers
I'll try to keep it as short as possible
What I want:
I want to run different operating systems at the same time.
I want to be able to switch between them fast.
I want all keys to work in the guest systems (I've had trouble getting along with VNC regarding this)
I would prefer if the host system is as stable, lightweight, and as unmodified as possible
Why:
To learn about different systems and how to set them up.
I want to compare services/daemons of the same type, such as e-mail, ftp, http.
I also believe in using the right tool(OS) for the right job
How:
I've read about Xen's GPU passthrough feature which interest me quite a bit, but I'm a little unsure how it works, from boot of the host to X in a guest.
I know you "hide" PCI/GPU interfaces at the bootloader stage. But if you for example hide the main GPU because you want this in your guest, what happens on the screen while the host system is booting? Is the monitor just saying "No signal" until the guest starts booting and takes over it?
If I disregard the GPU passthrough feature, I think I would need X on my host system. I read Xen either uses VNC or SDL to serve a screen of a guest. However, VNC isn't perfect with mod keys and mouse acceleration, and SDL requires X to be running at all times (host X crashes = all guest with SDL crashes).
So I was thinking if it's possible to connect to a running X within a guest, from my X running on the host, and use Ctrl+Alt+F1...F12 to change between the different guests running X.
I'm familiar with starting applications on remote X servers by changing the DISPLAY variable, but is it also possible to do something like
DISPLAY=xenguest1:0 xinit /path/to/wm -- :1
And then have the guest X on, say, Ctrl+alt+F4, while the host X is on Ctrl+alt+F3?
Previous experiences:
I've used VirtualBox and QEMU, but in both cases I felt the quest OSes were more temporary and targeted towards development on different platforms. The mouse pointer was also a bit laggy in QEMU, which I didn't like while testing graphical systems.

Answer 1

Is there a possibility to setup my TC so that I can connect my MacBook Pro via an ethernet cable to the TC without a connection to the wireless network router?
No, when the TC is configured to "join" a wireless network, it performs no routing functions...the Ethernet ports are not enabled.
If this is not possible, what can I do to be able to make the first backup via ethernet and then keep that backup on the TC and setup the TC as a part of my wireless network again (without connection to the router) ?
Temporarily, configure the TC using AirPort Utility - Manual Setup as follows:
Click the Wireless tab below the row of icons and change the Wireless Mode to "Off"
Click the Internet icon, then click the Internet Connection tab. Settings should look like this:
Connect Using = Ethernet
Connection Sharing = Off (Bridge Mode)
Click Update and click "ignore" to any messages that indicate that you do not have an Ethenret cable plugged into the WAN port and you do not have an Internet Connection
Connect an Ethernet cable from your Mac to one of the LAN <-> ports on the TC
Turn off the wireless on your Mac
Setup Time Machine again to connect to the Time Capsule and start the backup
In general, backups should occur at about 30 GB an hour, so a good time to do this might be overnight
When the backup is completed, configure the TC again to "join" your wireless network so that incremental backups will occur over the wireless network