"1 hot leg to float switch through on/off switch. Switch turns pump on and off.
One hot leg [directly -- and unbroken] through [the] on/off switch
other pump wire to ground."
1) You're describing what I like to call an "old school" trade practice. You'd be amazed at the stuff that was wired up that way. (Switching only one hot in a two pole/ two leg motor circuit.)
2) It's a very bad idea because:
a) It's wasting energy. The unswitched leg is constantly pulsing juice in and out of the motor windings. Even though it's not runnning, it's experiencing hysteresis losses thereby. For an ejector pump such a persistent bleeding of energy would entirely out match its primary function.
b) It's inconsistent with modern motor control logic. You're not going to catch a big price break because you're cheesing it on the number of switched poles.
3) Unless I miss my guess, you're going to need to install a safety switch within direct line of sight for this pump. The Code has really tightened up about disconnecting means.
Since my experience is biased by too much commercial practice, I might be too design-conservative.