The term "veneer" in a masonry exterior wall traditionally refers to a 4" thick masonry "veneer", a drainage cavity behind it and a back-up wall of some kind. Another newer system is gnerally called a "thin veneer" where a 1/2" to 3/4" thin layer of masonry is directly adhered to a masonry back up wall with mortar. The former is normally for brick on wood framed or concrete block back-up walls and where subject to freeze thaw cycles because it allows for water drainage and differential movement. The latter can be used with stone and concrete or concrete block back-up walls in warm dry climates. On high rise buildings a 2" stone cladding is usually supported by an elaborate system of stainless steel pins and connectors with a cavity behind it. What are you building?

Your property is so beautiful i can see why you live it. Your home looks like 80s contemporary style. Your brick is fine. The roof change is key. I don’t agree with metal roof for this style home. That look is more country, or traditional/farmhouse look. Not right for your home imo. I would recommend Weathered Wood HD by GAF Timberline shingle. Then once it is on, a nice coordinating color for trim and gutters etc will evolve. Your front door is hidden so select color for that last. A deep gold might look good. A dark color won’t do much for your front facade. So start with roof.

If an architect designed your addition they should be giving you guidance on the exterior cladding. If you don't have an architect I will spare you the lecture (although someone else may come along and deliver it) as the ship apparently has already sailed. I wouldn't be adding any stone veneer since you already have brick. Have you considered using wood (or wood-like) siding instead? This is a big decision - you should really be seeking expert local assistance with this question. Unless your builder is unusually artistic, he is not the one to be providing guidance.

Show more pics of the whole exterior. I'd be more likely to replace ALL the stone, or match another material ..... siding. Closest I can find........ top pic https://stoneplus.com/shop/colorado-blend-thin-veneer-flats/ Bottom https://www.k2stone.com/product/montana-antique-ledge-stone/