Dressmaker for Satin Gown: Alter + Add Shape Support

I am attending a wedding in the summer and the bride has asked us to buy from a select list of gowns. The dresses are all satin with little to no lining inside - fine if you are very slim but if you have curves they are all extremely highlighted.
I am a size 14 but with a large bust, so I have ordered a few dresses in size 16 to try, and would like to have my chosen dress altered to fit me. As part of this, I would like you to sew into the dress something that will support and smooth my shape: mainly my breasts and my stomach. AKA instead of buying shapewear to wear under the dresss (which I hate, and which I am sure you'd still be able to see as the dress is cream satin and lots of back and shoulder will be exposed), I would prefer the bra + shapewear to be built in.

My main aim is to make me look good and feel good in this dress, by making the dress fit and shape my body perfectly. If this is something you have experience in/have done before, please reach out!