Can I Replace Auqanot's Pedestal Pump w/a Submersible One?

I have an Aquanot II battery-backup system (the one w/the big, 25A charging unit). The pump is about 16 y.o., and not sounding quite the same as it used to. I like to be safe, so I want to replace it, but I really would prefer going with a smaller, submersible 12V pump instead of the big pedestal pump. I've never liked pedestal pumps in general; the whole concept is from 50 years ago, before they found ways to make reliable, safe (affordable) submerged pumps.

Is there any reason why I shouldn't use a non-Aquanot pump? I mean, a 12v pump is a 12v pump, right? I'd need to find a 12v switch, as the Aquanot pedestal pump has an integral, mechanical switch...but that shouldn't be hard to find. Or maybe I can set it up with the backup pump 'suspended by the outlet pipe about 20" above the pit floor; I think those pumps have simple water-sensors on them, so when they get wet, they go on.

Barring any reason not to do this, do you have any recommendations on which pumps to look at?

Thanks for your help & advice!

The problem you will find is that there is a very small market for 12vdc pumps, so the ones that are out there are for short term use, meaning that I would not want to have to count on it to work well or for long.