Another case for Powell MAX:
If the SW Corridor group decides on a MAX, the next corridor to consider this will be Powell. Let's look at the mall for a bit. That will put 3 trains on the East/West alignment and 3 to 4 trains on the N/S alignment: yellow, green, orange (and another potential line if the SW Corridor splits at Tigard and Tualatin). This means that both E/W and N/S malls will be close to their capacity threshold. Capacity is yet to be defined, so if anyone knows this please chime in.
At present the yellow and green run more or less every 15 minutes. This will slightly change when the orange line is added as trains change colors downtown. We'll find out next Summer what change this has on the N/S mall traffic. But the effect the SW corridor will have will be much more significant. 3-4 trains must be staggered at intervals every 5 minutes or less.
Enter the Powell Corridor. If Powell has one train, that places 4-5 trains on the N/S alignment, at intervals of 3-4 minutes. But what if the Powell Corridor has
two (or more) lines, one to Lents/Clackamas, and one via the existing alignment to SE Main and East to 181st/Gresham? By any definition of capacity, the N/S mall is antiquated.
If you are an advocate of a downtown subway, this is the most logical step. Given a Powell MAX alignment, a downtown subway will follow. Given Powell Corridor buses the mall will remain.