#1
Is there anything a Boss Line Selector can do that a foot-switchable effects loop cannot do?
#2
probably

what are your requirements? you could easily build any manner of line switching boxes to suit your exact needs
Get off this damn forum and play your damn guitar.
#3
OK I need to be able to switch the built-in reverb off, the chorus off, and activate the OD at the same time.

The chorus is in the effects loop, and the OD is in front of the preamp.
#4
You're complicating and making things harder for yourself. It's ok to use the amps reverb for cleans and distortion, set it at about 3 or 4 and you'll be fine. If you don't want any reverb at all, turn it to 0. Stick the chorus in the loop, step on it to turn it on/off. It's just one pedal, a foot-switchable effects loop isn't that big of a deal for only one pedal in the loop. You don't need to turn the OD on at the exact same time you're using the lead channel, it won't even need to be on every single time you use the amps distortion. When you're about to switch off the lead channel, turn the OD off beforehand and then switch to cleans.

It's really not that complicated. Calm down and wait till you've got the amp. Have the two pedals side by side to make things even easier.