I'm really looking to save pin counts and processing overhead which is why the analog sensors are so attractive.
Processing overhead is severe, yes. You could do it with interrupts if you don't need much resolution (a bit of wibble in the interrupt response time won't matter).
I write an Arduino driver that uses a hardware timer to measure the pulse length ("Timer 1 - Input Capture Unit"). That works nicely and hardly uses any CPU at all. Downside: You only get one of those pins per Mega328 and it takes a whole timer to do it (you lose 2 hardware PWMs).
nb. A Leonardo has a lot more timers and two pins that can be used for event timing.
Right now I only have 1 pin per sensor to dedicate so the only other choice would be to make them I2C ( All the SPI pins are used as I/O's)
One pin per sensor is all you need for that new version.
The other option is, as you note, to add another Arduino. Pro Minis are cheap and small and work well as very fast I2C slaves.