I have similiar relationships with both my small animal and large animal vets; and they will both let me have drugs and supplies that they simply wouldn't let the average pet owner have. In the case of the equine vet; this relationship was formed over years of working together, my assisting with clinic cases and surgeries and their teaching me extensively. However, this trust relationship depends on their knowing that I know when I'm in over my head and when to call them.
Even though my family refers to me as a "Vet without a portfolio" I don't consider myself a vet or even almost a vet. I probably have a few more skills than average experienced horseperson because of my experience and my relationship with the vets.
I guess if I lived in a remote enough area, having a centrifuge (the blood thing) would make sense; lots of breeders have portable ultrasounds, if you had enough stock on your place, your own ultrasound would make sense. A good microscope and the ability to do cultures and fecal egg counts, ditto. I'm having trouble imagining that having your own portable xray equipment would make sense for anyone. The training required to actually read xrays and diagnose anything other than a gross fracture is extensive, and it would also be hard to cost justify the equipment on anything other than a huge working farm.
As far as stitches and wound care? I know how to do simple suturing; staples are even easier, and the staple gun is fairly cheap. Again, if I lived in a really remote area, I'd keep suture material, a staple gun and surgical drains on hand, but I have good access to vets and prefer they do this work.
She can shoe, but we don't have the proper tools so we call the farrier
This is bizarre - a complete set of farrier tools is a couple hundred dollars, a little more if you need an anvil and hot forge. Way less than the cost of some of the other equipment you list as having. I have a complete set of farrier tools, minus the forge and anvil, so I can remove a loose shoe before it tears up the hoof wall, replace a nail, etc. I will do a *very* basic trim, but I simply don't have the upper body strength to do the rest.
Is your situation ridiculous? No. Wise? I'm not too sure. A good use of your time, money and resources? I doubt it.