How many do you need? n+1 (where n is the number of bags you currently have)
I have a few, my Billingham is my "daily" bag, I have an original slingshot 200 which is handy for a single body & a couple of lenses (typically a trip to London etc), a Lowepro rucksack for my long lens/wildlife kit, and a couple of other shoulder bags. I'm still looking for a decent smaller rucksack for two X-T2 bodies with lenses, flashgun and an additional lens. Can't find that one.....
Edit: Oh, and I forgot my roller case for holiday trips!!!
Whilst roller cases do help with the carrying I haven't found one that doesn't weigh a significant amount to restrict the amount of kit within and still be under the carry-on limits (unless you Fly BA of course!)
Think I'm up to five.
First was a Lowepro. Then a new Lowepro when the first got tatty. Then I rented a 500mm f/4 and needed something so got a Crumpler bag someone recommended. Then I bought my own 500mm and I got a Lowepro Lens Trekker 600 for when I'm out at the weekend (it's no good as a travel bag). Most recently I got a Think-tank Airport Accelerator for travel.
I miss the large front pocket on my first bag. Coats, lunch boxes, it's fitted most things. It seems all new bag only have slim, tight fitting front/side pockets.
I've got clik elite obscura 30 which I actually bought back in the day for travels with A99+70-400mm, 16-35 and a 50mm. It gave quick and easy access to A99+70-400mm. Also has crap loads for space to carry everything else when you are on travels. And its airline friendly (just the right size)
Now that I have bought a 100-400mm recently I may be thinking of keeping it. So better snap it before I change my mind
Only downside for you may be it not being able to fit a gripped DSLR.
I also have tamrac 5535 Adventure messenger bag which I don't really use at all...
I would think it would take a gripped 5D3, though not sure as I have a Sony A7R3 with L bracket in it, with a 70-200 f2.8 attached, a 100-400 , 24-70 f2.8 and a canon 16-35. I am very pleased with it, a comfy well-designed bag.
The padded liner comes out, apparently you can purchase extra padded liners for your landscape kit, portrait kit, etc I bet the liners are not cheap either.