The best long term solution, that would add value, would be to install the same type of hardwood for continuity. If it is site finished wood, then it is pretty easy for a good wood installer/re-finisher to install and do a pretty good job of matching the old floor. If you wanted to change the stain of all the wood floor in the house, then that would also be a good time to sand down everything, new and old, and re-stain in a new color. Don't use anything that is a fake wood-look and/or in a gray color!

We have hardwood on our main floor and LVP on our stairs down to the basement as well as on the basement floor (over cement). When the LVP was first installed on the stairs (it's been a little over a year now), my husband thought the "lip" part of the stair treads (the bull-nosed edge piece) was not installed perfectly flush and secure on several (I think 4) of the treads, so I wonder if that is not uncommon and is what your flooring contractor is worried about. I didn't even notice it, but my husband is a perfectionist and it bothered him. Rather than complain and have the installers come back to address the issue, my husband fixed the issue himself. I think he used tiny little nails (with no heads) to better secure the edge pieces to the adjoining LVP pieces, and I used dots of acrylic paint from my art supplies to cover the bitty nail holes. We have never had a problem with them since and we are up and down the stairs many times daily so they get heavy use. Just wanted to mention our experience in case that makes any difference for your decision. I don't regret using it on our stairs. We picked an LVP that coordinates pretty well with our upstairs hardwood in color, just a little more rustic which fits our basement vibe. We didn't want to introduce yet another type of flooring just for the stairs.

I would need more info but IMO mixing those 2 types of flooring is not a good idea. I would need to know why you can't do a proper transition strip just like any other meeting of 2 types of flooring. IMO bettert o get unfinished engineered wood and have it stained to match the rest .

I might be confused, but it seems the measurements in the black/white drawing are not the same as the measurements in the HD drawing. I went with the black/white for the overall dimensions and worked in the HD for the detailed. I just thought I'd go ahead and get something drawn up to hopefully spark some ideas. Maybe you can check on the dimensions. This is nothing revolutionary, but it will function nicely. All windows and doors left intact To increase natural light I'd invest in a large patio door (3 panel, 9 feet?) across the back of the dining room rather than remove the wall. And maybe trim back some trees and shrubs. 42" aisles Extra clearance on the window side of the island for 2-3 counter stools. Narrow pull-out pantry Fridge tucked out of sight, but convenient to the living room A lot of worktop and storage around the range Unfortunately, minimal amount of counter around sink but looks like the same in the HD plan