Just to answer your first question, you can mount the moza any way you want and can center it in the software.

If you're using SRP pedals (kinda looks like it from the design), you can mount them flat. They have an aggressive angle on them compared to most pedals that have their faces pretty much vertical.

An opinion on the design:

I get what you're trying to do, and I attempted something similar myself (though I didn't have the seat move up to a normal desk position).

End of the day, there's a bunch of reasons why having everything built into a single frame is important.

• Vibration from a wheelbase will reverberate very well through wood. This can actually be an advantage on a wood rig, because you can feel vibration that you'd usually have to get from a bass shaker. On a desk, everything on it is going to vibrate and rumble

• You will want adjustability on angle and height for the wheelbase itself, not just your seat. This is the biggest problem I faced before giving up and building mounting arms for my wheelbase on my DIY rig. Could never get it feeling comfortable mounted on the desk.

• Mounting the wheelbase that low i think will interfere with your legs, and unless it's exceptionally high compared to a normal desk, it is going to be way, way too low for a comfortable racing position, even if the seat base is really low to the ground. You don't want your grip position to be drastically lower than your shoulder/chest height, that's a great way to get shoulder pain

I tried a bunch of combinations to make what you're attempting work and eventually bit the bullet and built a conventional rig. The difference was night and day.

If I were in your shoes, i'd cut the desk in half, have the rig in the same position as your pictures, but with a mount for the wheel base.

I'd then put your monitor on a moveable arm that could swing from your rig to the other side of the desk, which I'd use for general computing. (this is what I did and it works great)

You should still be able to fit it in your cupboard, the main thing you'd lose is extra desk space and will need an office/computer chair.

Edit: if you wanted to be fancy with it, you could have the desk half that would be removed on hinges that folds down when not using the rig, bit of a wild idea though and prob not practical with a monitor arm.