I'm not totally with the "what was good for boaters 100 years ago is good enough for me" brigade. The market has changed, attitude to risk has changed and even those happy to live without separate "domestic" batteries, inverters and tumble dryers are probably still grateful for LED lighting and the cellular mobile network.
The winch on the boat trailer I used to tow had a useful function to stop people "forgetting" to engage the ratchet (AKA pawl) as they winched nearly two tons of RIB off a slipway.
With the lever in one position, you could wind the boat in, but you could neither wind it out nor let it free run.
With the lever in the other you could pay out line but not wind it in.
The lever had an "over centre" device so it had to be in one position or the other.
So you couldn't start to wind the line in without engaging the pawl.
I'm sure some bright engineer can design a pawl for a paddle with two positions - "Up" and "Down" - with it in the "Up" position it will allow raising the paddle with two hands and won't allow it to slip back - with it in the "Down" position it will allow you to lower the paddle with two hands or (in an emergency) allow it to fall but won't let you raise it.