The drive motor on a case is always last in every circuit case designed for the reason not to add a case drain. I was unable to find any hydraulic motor on the market that would handle that much back pressure.I don't know that I can tell you everything there is to know but let me give you my perspective more clearly: You're going to have a single pump providing output. You're going to use a priority flow divider valve to split out a specified portion of that flow to guarantee that the power steering unit always receives about two and a half GPM. So you now effectively have two circuits. Circuit A from the pump to the steering valve, circuit b from the pump to everything else. I don't see any reason you couldn't choose to run circuit b directly to the TCV and from the TCV to motor one and from motor one to motor two, and from there back into the tank. So all the fluid that passes through motor one has to also pass through motor two. I am unfamiliar with any caveats or difficulties of using that approach. You mentioned you may need case drains, and you could be right.
But the other approach that I know for certain can work, is to install another priority flow divider valve in order to split circuit b in half. So half of circuit b drives a TCV connected to the motor on the front axle, and the other half of circuit b drives a different TCV connected to the motor on the rear axle. One advantage of this approach is that you can adjust the proportion of flow between the two parts of circuit b. So you don't have to choose identical gearing and motor ratios between the front and rear axles. You can simply adjust the flow divider valve to direct how much relative flow to both axles to make them travel the same speed.
I would lean toward that method only because it makes it easier to find axle hardware that can work. And because I don't have any ambiguity about it having idiosyncrasies or caveats.