Four solid pillars supporting a hefty top plate would work well and be bit more versatile.
Maybe 1/2″ – 12 mm steel plate for the top, 1 1/2″ – 35 mm alloy for the pillars with both ends tapped for the same thread as the T-nuts sized to fit your slots. Short studs on the bottom ends of the pillars so they can be screwed into the T-nuts. Countersunk cap heads to hold the plate on so nothing projects through the top.
Drill or tap top plate as makes sense for your work. I favour grid of holes, maybe 5 spot dice patten on 1″ – 25 mm centres for 1/4″ or 6mm bolts, for convenience in holding small work. For most ME sized work simple home made clamps made by bending 3 or 4 mm steel into an L shape and drilling / slotting for a bolt work pretty well so long was you don’t get over ambitious with cuts or feed. Take up less room than the usual bar and step block type. No great loss if you have to cut one ‘cos its irredeemably in the way because a replacement is easily made.
With post and plate you can have two sets of posts of different lengths. One set for when you are working with parts held in the vice and one set for parts clamped to the table, via a sacrificial plate if need be.
Clive