been called a lot worse than that here!
You present trailer is toting a load of 250kg tops, your new rig is going to be a good 250kg more 200 for the hull and 50 for the engine (e &eo) so I'd be looking for a much beter winch and strap. Also if you are going to use the edge of slipway technique then your strap is going to have more strain put on it, I think the loading at 60 degrees is a factor of 1.5. I'd want a strap that handles at least a ton therefore I'd go for a winch with a 1.5 ton capacity (if it fits your trailer) as this will be easier to winch in lower gear.
I have used electric winch's providing you can get the power to them they are fine. I'd put a dedicated battery on the trailer and charge it from a second socket on the tow bar. Be careful of the remote contacts corroding, pay special maintenance attention to these and take the pot of Vaseline and apply it liberally to the contacts.
Id also consider fitting a couple of launching rollers to the back of the trailer I'll see if I can find a picture of what I mean.