Minkey, I can't disagree with you because I have not walked before Leon.
When we were deciding on what to do, we considered Roncevalles to Longono, bus to Astorga and then to Santiago. People told us if you have to cut something out, cut our the meseta.
If you KNOW you are going to come back and finish the
Camino Frances, so you are committed to doing it in parts, I agree that it would be best to wait and get your compostela on the last leg. But if this may be your only time to go on the Camino, I think going to Santiago is best.
One day of flat walking out of Leon I am sure is not the meseta, but some of those that we walked with out of Mazarife said "Just imagine yesterday, for an entire week, in the mud".
As Minkey has stated so eloquently before (and you should take this to heart) each person's Camino is their own. Our inputs may help shape your introduction, but only you will experience it.
But we were very happy with our choice and have come back feeling accomplished and ready to go back and start in St Jean (my daughter may have outher ideas!)
Rambler