You can also use a dual-controller power pack.
But what you really need to design into your plan (as I am doing now) is electrically-isolated blocks of track. If you have two loops, for example, isolate them at the crossover(s) with the little plastic track joiners. That way, you can have one controller running the inside loop and the other the outside. When crossing over, just set the controllers to the same speed. My previous layout (bought second-hand) was wired that way, and it was very simple.
This can get as complex as you like (I am planning 11 blocks, and am considering up to 4 controllers) but you end up with a lot of operational challenges -- but then, some of us like that. You have to keep ahead of each engine, making sure that the block that it is using and any that it is headed for are all set to a single controller. I wish to add colored LEDs in the system, so that I can tell at a glance which controller (red/green/blue/yellow) is in change of each piece of track. But I have not yet figured out how to wire that in line with the controller selector switch. I may scale back to two controllers just to keep the wiring managable.
Anyway - what you are looking for is certainly doable, and should not bee too difficult. I may even have a spare dual power pack if you need one.
There are many here who will encourage you to move to DCC, but I am in the same boat as you - I've already spent to much money on this effort, and a DCC conversion would set me back another several hundred dollars.