Split HVAC System question

We’re at a crossroads, advice needed from the standpoint of efficiency and regular maintenance access. Don’t care if we have to patch holes. House is two stories, 1400sqft, 100 years old.

Our furnace is in the basement and feeds duct work that is either on the floors or on the walls about baseboards (depending on room). It’s 22 years old.

Our AC’s condenser is broken and the air handler is in the attic with vents on the ceilings of rooms.

With the age of the furnace and the condenser broken, when the time comes would you:

keep the systems separate or; combine the two systems in the basement having heat and ac come out of floor and wall vents?