3 volumes and 1 tone with no switches means there are four pots constantly in the circuit, regardless of which pickup(s) is/are turned up or on. This can cause the loss of some treble/highs to ground through the pots. Also, it affects the loading on the pickups which potentially changes how they sound compared to what you expect. Additionally, to mute the bass you'll need to turn down all non-zero volumes, which will be a pain if all three are up. Just my thoughts.

The two toggle switches would work like this:
Toggle switch 1 selects between bridge/bridge + neck/neck
Toggle switch 2 selects between middle/middle + toggle switch 1/toggle switch 1

So, the layout would basically be:
bridge pickup -> push/pull volume -> toggle switch 1 in A
neck pickup -> push/pull volume -> toggle switch 1 in B
toggle switch 1 out -> toggle switch 2 in A
middle pickup -> push/pull volume -> toggle switch 2 in B
toggle switch 2 out -> master tone -> output jack

(if you can understand my awkward explanation)