I haven't faced your exact, quite-interesting problem in my plumbing of Trailers and Rental Properties, but here's a few ideas that might help.
1. Two - A -> B Valves plumbed in series can permit the 3 connections you want; just not all in one Valve. The first Valve can select from 2 'inputs'. The 'output' of that Valve can then be 1 of 2 'inputs' chosen at the second Valve, the 'output' of which can go to 'whatever'. Of course, Valves don't care about the direction of flow going through them. 1 or both of these Valves could be electrically operated manually, if they're tucked away somewhere, or could energize automatically at the same time as the Pump.
2. Check Valves that allow flow in only one direction are used in Hot Water/Solar Plumbing, Radiant Floor Heating and similar applications. Perhaps they could prevent backflow into your Tank if/when that line, or another line, is pressurized from the other side of these Check Valves.
3. 'Conductance 101' tells us that several smaller Tubes will pass the same flow as a single 1" Tube when filling your Tank. Perhaps you can locate a new Fill Port w/Overflow Tube and improve upon whatever existed before while modernizing your System and simplifying maintenance. So long as they're connected together near the floor, several Tanks can be interconnected.
4. Gentle 'sweeping' Elbows restrict flow less than tight, 'hard' 90 Elbows. Keep this in mind should you plumb several parallel Tubes together as a Fill Tube.
When I tackle a project like this, I sit down and imagine what 'Murphy's Law' situations/oversights could flood me out if/when I get distracted. For example, on a Cistern project of mine, I flipped over Rain Monitors designed for 'pausing' Sprinkler Systems so I could shut off Pump Controls when the Cistern Tanks topped off full.
Other interesting upgrades...