Try different photos from different angles. Or maybe Emily here on Houzz will weigh in. Or Celery Renderings. They do nice work.

This was as good as I could get AI to corporate. Take Diana’s advice and post some additional photos further back so we can see more of the space.

From just seeing the pics you’ve provided, I would consider adding interior windows so you don’t lose all of the natural light in that space.

We have seen similar projects done on these forums a few times, if you go back to the late 2000's.

Most important is how high are the ceilings overall? How high will first and second floors be when closed in?

Will you be able to add windows in the new bonus room?

Here is one where they closed in a 2-story kitchen and added a master suite above.

https://www.houzz.com/discussions/2580398/no-more-two-story-kitchen-my-addition-with-pics

IMO get the architect to design it and they will also do some renderings . Please do not ressurect old posts since none will be exactly like yours anyway. The first question is always how high are you ceilings now where this is planned and know that the HVAC will aslo be affected not to mention the budget and the mess.