Aso-Takachiko-Beppu-Fukuoka 4 days

Hi
Most of the itinerary on the forum are for 9 days or more
Wish we had the time!

As we only have 4 full days and we are big nature lovers, we focused on selecting 3 key places and doing self drive, would like to check with experts if this is doable:-

Day 1
Arrive Fukuoka by JR from Osaka in Morning
Drive to Mount Aso 2hr 30min / Sightseeing
Stay Aso Ryokan with hot spring (any recommendation for in room hotspring in this area?)

Day 2
Drive to Takachiho Gorge 1hr 20min /Boat Tour
Stay the night in Takachiho or should we push on to Yufuin?

Day 3
Drive to Yufuin/Beppu 2hr 30mins
Stay in Onsen / explore Beppu Hells

Day 4
Drive back to Fukuoka and return car 1 hr 30mins
relax rest of day

questions
1. For Aso and Takachiho, where should be the best places to spend the night?
2. For the above which limit driving to 1 or 2 hrs per day - is there any enroute interest points we can still fit in?
3. As alternate, would Sasebo islands and Huis Tens Bosch be a better fit than Takachiho?

Many Thanks!!

How about the trans-kyushu route?

The last I heard, the area around the crater is still closed due to poisonous gases. You don't say when you are leaving - but you might not be able to get near there. Since you're driving though, nearby is Daikanbo which is a spectacular lookout over the whole area. There is also Nabegadaki, a beautiful waterfall just NE of Oguni Town.
If you love nature and want to see it, why not stay in Kurokawa for a night? It's a famous hot spring area and known for its beautiful forested area and outdoor baths.
You could see Takachiho in several hours and drive to Yufuin if you like.
https://www.youtube.com/watch?v=H49x41ViFJk
Along the way if you have time, you might see Usuki for its famous old stone Buddhas.
The trans-Kyushu route would be the way to go, and would take you to Beppu:
https://www.youtube.com/playlist?list=PL7LcPcmoSg-hOggZamc2lUNTr46ApKX...
From there you could go to Yufuin - but you might be overdosing on hot springs.
Finally, Fukuoka has a number of good sights to see. The Nanzoin temple alone is just 20 minutes by train from Hakata Stn and is an amazing place (and free):
https://www.youtube.com/watch?v=lT4VQFmHFyM
There is also Ohori Park, Canal City, Nakasu, and many other places:
https://www.youtube.com/playlist?list=PL7LcPcmoSg-j4RLa6iC7ayvBAbOn8-0...
http://www.thejapanfaq.com/fukpic.html
As for choosing Sasebo & Huis Tens Bosch, it is all up to your interests of course. It would also mean a lot more driving and wasted time. The pricey HTB looks very nice, especially in tulip season, and many say authentic, but aside from that it is mostly a Potemkin Village. The cruise around the islands sounds quite relaxing though. For time though, I'd stick with Takachiho.

Thanks for your suggestions, Ken

I will be travelling 17 dec till 20 dec
Will revise my itinerary as follows:-

17 Dec
Drive from Fukuoka to Takachiho
Stay 1 Night

18 Dec
Drive from Takachiho to Mount Aso
If closed stop by Kusasenri+Komezuka+Daikanbo
Stay 1 Night Kurokawa

19 Dec
Drive from Kurokawa to Yufuin /Beppu
Stop by Nabagataki Waterfalls
Stay either Yufuin or Beppu
Is it worth to stop by Mount Kuju - is there a similar viewpoint like Daikanbo for Mount Kuju?

20 Dec
Visit Beppu Eight Hells
Then drive back to Hakata and return car