R5 vs R3 for a second body on safari?

At the end of July I'll be going on safari in Kenya and Rwanda. This will be our fifth safari, so I'm used to the routine. My plan is to have two bodies - one with my RF 600/4 and one with the RF 100-500. That combo has worked well for me in the past, but I need to pick up a second body.

My current body is an R5. I do have both the R1 and R52 on preorder (and should be among the first delivered since I preordered over a year ago at my local camera store), but it's looking increasingly unlikely that either body will arrive before I leave. I still have time to wait for an announcement to have a better idea, but I'm now coming up with a backup plan.

In the past, I've just purchased a camera - usually used or refurbished - and sold it after returning. My default choice is another R5. That's exactly what I did on our last safari to Zimbabwe and Sabi Sands and it worked very well. However, I'm debating whether to mix things up a bit and bring an R3. The following are my thoughts in favor.
  • Although I do crop heavily with my R5 today, I do have a 4'x6' print of a crop from a 1Dx3 hanging in my living room of some elephants from Tanzania, and the detail is incredible. So, I know I can still get good things with 24 MP.
  • The R3 will handle low light much better, which can become an issue early mornings and late afternoons. It may also prove useful for gorilla trekking, where whichever camera will be paired with a RF 70-200/2.8.
  • The R3 has better AF as I understand, and its eye focus is promising. I'm familiar with the haptic controller from the 1Dx3 and greatly enjoyed it.
The disadvantages are:
  • 24 MP vs 45 MP
  • I haven't used the R3, though I did once have a 1Dx3.
  • It's more expensive and niche, so it may be tougher selling it when I get back (and I will sell it in favor of the R52)
  • The batteries aren't the same, so I'll have to buy an extra battery and bring another charger. The charger for the 1Dx3 was huge because it supported two batteries, which was problematic when packing for bush planes (and I already have a ton of gear because my son is bringing his C70 + lenses)
Any recommendations? I'll probably wait at least until the end of June before picking up anything in order to give time for more news on the R52 release.
 
The disadvantages are:
  • 24 MP vs 45 MP
  • I haven't used the R3, though I did once have a 1Dx3.
  • It's more expensive and niche, so it may be tougher selling it when I get back (and I will sell it in favor of the R52)
  • The batteries aren't the same, so I'll have to buy an extra battery and bring another charger. The charger for the 1Dx3 was huge because it supported two batteries, which was problematic when packing for bush planes (and I already have a ton of gear because my son is bringing his C70 + lenses)
All valid disadvantages, IMHO.

I moved from 5D3 to 1Dx to R3, and it was relatively easy to move. Surely the jump from 1DX to the R3 was the biggest, simply from the complexity of the menus. But in the end the menu system is pretty consistent across the models so I don't think this would be considered a show-stopper.

The R3 battery charger is very much like the 1Dx3 charger (dual-battery and huuuge). You're likely to take a bigger hit on the resell of the R3 vs the R5.
The R3 can be charged through the USB-C port using an USB-PD charger (the manual refers to USB Power Adapter PD-E1, but any 65W USB-PD compliant charger should work).

Maybe there is the option for renting a body for the duration? (I did look into this at one point and learned it wasn't financially sensible to rent a camera for 7-14 days).
 
Another R5 will give you two cameras with the same user interface, which will be more convenient.

Personally, I would also consider getting an R62 and putting the 100-500 on it for a nice lightweight setup when heavy cropping is not needed (you will have the 600/4 with the R5 for that).
 
I have both the R3 and R5 and shoot mostly birds. I have been shooting birds in flight since the 30D came out and when I don't want to miss the shot as it's a bird I really want, I go with R3 every time. Best auto focusing camera Canon has made to date. If you crop a lot, R5 when it's important or fast or lower light, the R3. Actually I would give up the 45mpx for the lowly 24 from the R3 if I had to part with one of them. :)