Some ideas about flexible systems:
Over the last while I've been thinking of down sizing my fleet because I want to move and build a smaller house so I've been looking at my touring/riding needs in three sort of ways. Paved, groomed/nice gravel, rougher gravel/off road. I've moved into lightweight trips so heavily loaded isn't that appealing any more. Along with touring I also enjoy trail riding, weekend rambles and commuting so my goal is to get down to three bikes and a couple of projects that come and go.
With paved roads I have a very enjoyable 700c touring bike and have decided to buy a second 650b wheelset with 40mm or so tires to cover groomed gravel riding.
That checks two boxes with one bike but still leaves rough gravel/off road.
For a while I've been experimenting with my trusty old rigid mtb/converted touring bike as my heavily loaded and off road rig. It is rugged and a mule for climbing and hauling with it's upright posture and low geared triple crank. I've swapped out the rigid fork for a suspension fork and put some aggressive tires on it and it has served well, but the lack of ultimate tire width is an issue. Some places I want to go could use some more width than the 26x2.4 max I can get away with.
Over the weekend I finally resolved the issue by buying a fat bike and am now in the process of converting it over to a dedicated trails/bikepacking rig by refitting a lot of parts off my other bikes like saddles and bar ends. This will leave me with two bikes and three wheelsets for all conditions plus my Fixed Gear which is just fun to ride = 3.
The bike as purchased:
I managed to fit my Filzer PR-4 rack and only had to cut a small part of the bungee stay so it would clear the brake lever. To finish I plan to get some titanium bolts and thread them through form the inside so they can be removed if sheared.
I've also added a Blackburn cargo cage to the downtube which clears a 1.5L Nalgene bottle.
Another plan is to share one bag system between both bikes, adding and subtracting as needed. These are basically Blackburn
Outpost, Carradice
Carradry and a MEC 25L waterproof backpack. I tried a seat bag but with the sprung B67 it hangs too low and rubs the rear tire when the seat is dropped for trails.
Trail riding:
Semi loaded:
Fully loaded:
Both bikes also share the same removable lights