That is pretty freakin awesome, and by the looks at what the others had left behind, you will be very welcomed in that area. Mikey might have just found another GOLDEN spot for a carpet cleaner with passion. Keep it up and you will become the household name.
I don't know why these ugly buildup jobs aren't cleaned using a Turbo?? I did a mosaic nearly identical to this one in a remodeled restaurant, applied a good stripper cut 4:1 short dwell time of 12 to 15 minutes agitated with a carpet groomer brush just to keep low and high areas on equal exposure to the stripper. Then I hit it with my truck mount set at 1800 psi with no heat and years of black grunge under wax layers was gone. no floor machines no abrasive pads (I've see a black pad scratch up a glazed porcelain) Just a steady walk with the spinning spraybar from my Turbo.
Mikey don't you own a turbo tile tool or other spinner? I almost never use a floor machine or abrasive pads to pre-agitate. I've done some scarry buildup and coatings in 28 years and find that the right chemistry, heat and pressure makes me move fast and efficient. Coated tile, slate, sandstone, limestone, porcelain, quartzite, pavers, vitreous clay, quarry and many other surfaces just power clean if the cleaning pie is complete.
my rig goes to 3200 but my average is 1800 for nearly all T&G.. If the grout is going to fail then it was bad when it was installed. I run across that issue once in a while but discover weakness when I do the preinspection. That's when I see the opportunity to do repairs that some jobs have anyway. Cracks. holes, and missing grout. The customer has been trying to find someone to repair for years and I usually do for free especially if I end up color sealing.