I use Expidit and Bonde, both from IKEA. The Bonde is nice as a 1 shelf wide by 4 shelf high tower that is perfect for tight spaces. The Bonde comes with a back on it where as the Expidit does not.
I have 2 Expidit units in the room where the RCM lives, and I have 2 Bonde units on their sides and stacked one on top of the other in the listening room for those LPs that are in the current "heavy rotation".
Both Expidit and Bonde have proven to be, over the years, the best value per dollar in LP/tape storage
If I was thinking of adding casters to a large Expidit, I would think that at least 6 per unit would be needed. Unless you have a big open living space, I would think that trying to steer a fully assembled and loaded Expidit around, might be pretty tough (remember - the Expidit does not come with a back on it)