Change of plans- how many bathrooms do two people need?

Hi There, Jennifer here with a quick update on the Tate Residence construction.  Framing was supposed to happen today but it is currently pouring rain, we are going to get 4 inches!!!! Needless to say the framing has been rescheduled for next week.  It seems like we can't catch a break with the weather, the Farmers Almanac says this summer is going to be crazy wet and crazy hot.  I refuse to complain about the weather since it is what it is, but here's to hoping for a dry summer!!! Now that the framing is imminent and plumbing roughing is also happening soon we need to be 100% set on our floor plan.  Our current floor plan has our powder room on the left side of the house by the study.   

   My sister Faith from day one said she didn't like the placement of the powder room as she thought it was too far from the kitchen and family room.  It would be annoying for potty training kids.  I obviously don't think like a mom since we have no kids yet but she is a mother of (almost) 4 children so she knows what she is talking about.  Andy asked my mom what she thought (mother of 5!) and she said we should put a powder room in the mudroom by the backstairs and side entrance since that is where the heavy traffic would be.  Our mud room or "drop zone" as some architects call it is fairly large at 10 x 24 feet so we do have some wiggle room to play with.  Below is the mudroom without the powder room.

Andy redrew the mudroom to scale and added a powder room in the mud room by removing the closet and moving the pantry.  See Andy's rough drawing below. 

The total cost of adding this extra powder room will be around $1,600 which is fine.  However by adding this second powder room I feel like the other powder room loses its value all together.  Andy said the original powder room on the other side of the house will be the "formal" powder room.  Since I really don't think we will have such formal affairs I want to reuse the second powder room.  My idea, which Andy is not sold on is to connect the powder room to the study and add a shower/tub so we will have a potential 5th bedroom or small first floor master with its own private bathroom.  The only changes we would have to make would be to add a tub/shower since the toilet and sink are already in the plans.  I think this well help for resale since 1) It adds another full bathroom 2) it adds another bedroom 3) We could always use the sitting room in the master as a "study" so we don't really lose that space 4) First floor master options are very valuable for buyers who are older, as they want a house they can grow old in, having a bedroom/bathroom on the first floor would mean they can move downstairs when the stairs become too much, my parents who are still very young are looking for homes with first floor masters so they will have this option in 30 years instead of going to the old folks home :) 
So let us know what you think, I need help convincing Andy!!!