Home base recommendations between Cordoba and Granada, Spain for 4-7 days

Cordoba is pretty central location to travel to all points

I can't think of any. It's just too far - even with a car - to make day trips worth it, especially since it sounds like you want to include Cordoba and Granada in those day trips. Trains can be expensive and there aren't many - for instance Cordoba-Ronda, even as a day trip the day after tomorrow, the round-trip ticket is over €50 per person, the ride takes nearly 2 hours, the earliest train leaves Ronda at 10 am and the last train departs from Cordoba at 5 pm. That gives you a mere 5 hours to sightsee. A brief internet search leads me to believe there are no direct buses between the two cities.

I've spent 2-3 nights in Ronda with a car, once from Jerez to Granada, once from Sevilla to Cordoba. The purpose both times was to spend time in Ronda and visit the pueblos blancos.

My apologies, but I find convoluting travel plans to include numerous day trips to save a bed change is false economy....both of time and money. Both these cities need more than one day, and in my mind, can easily use 3-5 nights. I understand the weight of schlepping luggage, but Spanish taxis are clean, metered and well priced. The caveat, is don't choose lodgings in Old Town Granada unless you are certain taxis are allowed to drop you at the door. Up in the Albacin, traffic is limited to certain hours of the day and some streets are too narrow for 4 wheeled vehicles.
If you have your heart set on your plan, however, Baena is about half way and travel is by bus. Comfy and a little cheaper. I can't find the new train route map that opened up last week, and Rome2rio still shows the route as bus. If you can find the stops on the new route, then consider one of those stop cities.
Antequera is a transit hub, and would allow you to include Malaga as a day trip, but it is still 2.5 hours from Cordoba.

Actually, Antequera is only 30 minutes from Cordoba by train. It's also a decent base for day-trips to Granada and Malaga. Osuna and Ronda are feasible, and perhaps for some even Sevilla. But Cadiz is really too far.

Antequera is a nice town, with a few worthwhile sights of it's own and a good place for evenings paseo and eating. It's very Andalucian with limited numbers of us foreigners staying overnight.

However, there are practical problems, which is why some don't suggest Antequera as a home base. You'll need to decide if these are deal breakers. Firstly, the fast AVE trains actually leave from Antequera Santa Ana station which is about 20km from the town itself. So you'd need to factor in time and taxi cost. Secondly, services by coach and train from the city itself exist but may not be frequent. So in practice you might have to get up early for a day trip or only have a few hours in your destination before turning back.

I picked up Frommer's Shortcut Andalucia out of curiosity for travel options. Published 2015. I wonder if they have a new edition.

"Granada is well served by more buses than trains to virtually all major towns in Andalusia." CHECK: www.alsa.com

Nick, the Antequera 2.5 hr estimate is by bus and from city centre. As you mentioned, the train logistics make things a challenge. I looked at it as an option when planning 2 years ago, but the cost of lodgings and the public transit had me drop the plan. I prefer short let apartments and they were more expensive than I anticipated. If I understand it correctly, it is a bedroom community to Malaga and known to be relatively pricey. It has sk e ancient dolmans in the area, and national parks, but that means needing a car as well.

With trains running now, some of those Granada buses may evaporate. In any case, what's viable for moving from one base to the next is not necessarily practical for day-trips. I do not like changing hotels, but on my current trip I ended up sleeping (always for multiple nights) in Ubeda, Cordoba, Seville, Cadiz, Ronda, Malaga and Granada. I would have much preferred fewer hotels, but that's what I needed to do to (mostly) avoid day-trips requiring close to 4 hours on trains and buses.