That is going to be a bit risky for you. As vct is designed to have a topical to protect it. If you have ever had a new piece of vct in your hands it is very flexible until you reach a point and it cracks or tears. I believe the flexibility it has is because the factory applies a coat of finish to the vct before it leaves the factory as a protector while it gets shipped, handled, and installed.
Armstrong, one of the larger vct manufacturers,reps always pushed us to make sure their floors had at least four coats of finish and if at all possible five coats would be better. The primary purpose of floor finish is NOT to make the floor shinier it is to protect the vct and to provide a level of anti slip resistance to the floor while making it easier to keep clean on a daily basis, ie that is why super markets, gas Station, school and so on, opt to place vct as the flooring of choice.
In other words, you need to express to your customer that yes you can strip it and leave it bare, but it will leave the vct very week or fragile. Anything with any weight dropped on the floor will crease, crack, or gouge the floor quite easily. If he doesn't want shine there are matte finishes without shine that can be applied.
For the stripping, if it is indeed a true sealer that is on the vct you are going to want a hard hitting stripper like bare bones by Ncl, or prostrip by diversey as a degreaser will not remove it. If the goal is to remove all the sealer, then you will need to go with a black pad, I would recommend you go with a 3m high productivity pad as it doesn't leech or bleed black gritty material from the pad as most black pads do.
Without pics of the floor, an option could be to use 3m spp pads with just water before you even try to strip with the alkaline, but again I don't know what you are dealing with there. The problem will be if there is too much finish or sealer, when dry it might show some low points where the spp pads didn't quite get all of it off.
If you have any questions feel free to give me a call 817-829-4708 Michael