First, I don't think we ever waited that long for our luggage. The bus that picks you up for the car rental can take your luggage. If you need help getting it on the bus there are the two of you plus the driver will help. We tip the driver but many people don't do it.
I wouldn't want to take a chance being separated for many obvious reasons. It sounds like you are new to the area and that makes me feel even stronger about sticking together. You could lose more time with him trying to get back into the airport to pick you up. It's a big place and very crowded. What if he got into an accident doing this by himself trying to get back to you from the car rental. I'm not wishing anything bad to happen but things happen all the time and being separated from each other is just not a good idea. Also, two sets of eyes are better then one set with traveling because one can concentrate on driving and the other can navigate and look for signs, etc. to proceed.
If you insist on doing it the way you are thinking about I would be very specific where you are to meet up. Don't leave any doubt about it. Also, don't be suprised if a cop or security is upon you if you are not very quick about it all. I think this is a more stressful way to do it but each to his own. I think you are trying to micro manage the trip too much.
