Old home needs some help
So I have an older home that was built in 1970. My current system has trouble keeping up with the 2nd floor, the A/C specifically. I am debating tearing out the duct from the chase that runs from the basement to the 2nd floor to run gas, line sets, power, and a drain to the attic for a 2nd unit that would only serve the 2nd floor. The alternative would be a mini split system with ceiling cassettes and a heat recovery box so that I could individually control the bedrooms. The second floor is about 1100 sqft and the attic has pretty good space with a little over 6ft at the peak of the roof. I do not have an attic ladder or great access currently and don’t really have a great spot for anything permanent. I can however cut a hole for access in one of the bedrooms that would be patched and just reopened for the inevitable replacement years down the line. I am a commercial GC by day and formerly a carpenter by trade, so creating access, building platforms, patch and paint, etc. is not really of any concern, that can all be handled by me.
I am looking for advice on what system style would serve my home best, and any additional considerations or suggestions that you all may have.