If you’re concerned with frame flex and sag, removing the leveling feet will remediate a large majority of those characteristics, However as stated by @mikep, your bench/table/torsion-box base becomes additionally critical and you lose the leveling ability the feet provide. These characteristics are logicially more pronounced in the larger machine footprints.
There’s a Shapeoko Users Group initiative for aluminum base plates for the XXL if you’re interested in moving toward a stouter machine platform: