How about this for knowing how much water used from tanks

[SambOz]

Amazing how long water lasted when it came out of a 20l plastic drum or accessed in a Van by a hand pump.

Being in the K.I.S.S. camp things like this are just another thing to cost $$'s and break down 

[tryagain]

Amazing how long water lasted when it came out of a 20l plastic drum or accessed in a Van by a hand pump.

Being in the K.I.S.S. camp things like this are just another thing to cost $$'s and break down 

You can still use these with a hand pump just lets you know how much water you have left which I don't think is a bad thing, probably allow you to better analyse water consumption and therefore make your water last longer. If it does break then your just back to the KISS method of guesstimating.

Most things to do with a camper trailer are about making the experience better, you could use your KISS argument to write off anything above a swag in the boot. The levels of convenience people want to best enjoy the experience of getting out camping will vary from one situation to another, none are necessarily wrong or right as everyone's situation varies.