Christopher,
So far, the OEM arrangement has worked fine but, as a matter of principle, I like to have easy access to all the important parts.
You are correct about the removal of the cover being a fairly quick process because I have replaced the screws with hex-head fasteners and I can remove them in a jiffy using a simple speed wrench and socket.
However, if a loose object, like a propeller shaft free of its coupling or an alternator broken free from its mount, damaged a drain hose in rough seas, seawater could flood the bilge faster than I could remove the cover and close the valves.
Also, I have replaced my other through-hull fittings with proper seacocks with flanges that are through-bolted to solid fibergalss backing plates and I have been seeking a way to do the same for my cockpit drains but maybe a mushroon fitting and a 90 degree elbow is good enough.
I am looking forward to seeing your solution. It sounds like upgrading the parts in the current configuration might be the best idea.
Keep us posted.
Thanks,
Dave