I have been experimenting a bit in that I have developed negatives to print on both the Lodima grades. Thus far I have not seen problems with either grade, but the number of prints made is not sufficient to draw firm conclusions. No issues either with the "trial run". I believe I will most likely proceed as you intend, i.e., develop negatives to print on the Grade 3, with water bath development and the Grade 2 "held in reserve" as necessary.
I have ordered the Fomalux. Will not have the chance to use it for at least several weeks ( at least a week go get here )...but I will try to print the same negative on both grades of Lodima AND the Fomalux FB, and report to the thread. Unfortunately, I have no scanner-and no current plans to buy one!
With the Fomalux RC and the FB one might have a way to "proof" one's negatives at a very significant savings. The print exposure is apparently quite different, but at least one can use a NaCl paper and Amidol.