Thanks
BillBurn! Based on your additional information, I feel like staying at the RC that extra night just makes sense. I'm weighing a 1 hour journey from Osaka hotel to KIX, versus a 2 hour journey from RC Kyoto to KIX. If I were to travel from RC Kyoto to Osaka the day before, I'd basically be killing the latter half of my day in Kyoto, as well as only making time for dinner in Osaka. So with all that said, and knowing there is an easy direct train from Kyoto to KIX - it just seems more sensible to get 1 hour less sleep, but several hours more productivity, by staying at the RC Kyoto for that last night.
Particularly as it's still booked at the 60k points redemption rate! I do really want to see Osaka too - but no matter which way I cut it, I wouldn't be getting more than just a dinner there anyway. So Osaka can wait until next time.
Thanks again! Especially for the more detailed information on bag shipping costs. I think if I had more than 2 cases, I'd probably be inclined to take up that service - but I should be able to manage 2, and imagine the trains have luggage racks.
One more question if I may: do they have Uber in Toyko/Kyoto? Is it the 'done thing', or do people just to tend to hail a street taxi locally? I'm very worried about the language barrier!
No Uber as of my visit last year. However we've never had an issue with taxis. Take a few business cards from the hotel (address is in Japanese and English) so you can always return. If you have internet access, all the mapping software will display a destination in Japanese that you can show the driver. It's easier than you think.