I like the way you have the stand built. I love Kreg units and own two myself. My first concern is that you won't have enough room for the skimmer, either removing the cup or with getting the pump out for cleaning. If you have enough room for that, you should be good.
I have three problems with your wheel theory. My first is that you would move the tank for a furnace or HWH replacement/repair but those would have to go through the doorway. If you have room in front of the door anyways for accessing the furnace room, anything that would necessitate moving the tank would involve RIPPING OUT THE DOOR
! I don't know about you but if they were going to take a door out of the wall to fix something, either the door is the wrong size or I would want to move the tank away from the demo.
The second counter to your moving the tank theory is that you're assuming you will need to move the tank at some point in the future. I would counter that by saying you are more likely replace the tank or have moved before you will need to do that kind of work on the furnace. Most furnaces and HWH will last decades, very few reef setups last that long.
My third issue with the wheels is that they don't give you any way to level the tank easily. If there is a slope on the floor, the tank will not sit even which could result in things leaking or bending over time.
If you decide to remove the wheels I would recommend either placing the stand flat on the base sheet of plywood or to move the filler strips you have between the wheels out until they sit below the sides of the stand. You want the load to go straight from the top of the stand, down the sides, and into the floor. Having the toe kick is all well and good but it makes for a poor load path.
The result is a very clean design. Looks good so far. Keep posting picks. I look forward to seeing how this progresses.