Yes, I  have to use flash light to see the seacock and open the cover that is below the mattress. My mattress is always folded back, so access is no problem.
If you are considering installing a ball valve elsewhere, you will have to remove the existing seacock and connect a new hose to the through-hull directly. This means the through-hull must be replaced to accept the hose. 
In my opinion it is not worth the cost.
I wonder if a new seacock can be installed under the seat in front of the table for easier access.

I agree that the location of the pre-2005 raw water seacock is not ideal, especially after just upgrading from a C30. For the next haulout, I've been thinking of moving the thruhull and seacock to where it is for the the 2005+ hulls, and adding an access door of some sort. I would fill the old location as well.

The main unknown is where the strainer is on the 2005+ boats. Is it also moved toward the starboard side of the cavity to reduce the hose run and suction resistance? Or is it still on the port side of the transmission and prop shaft like my 2004, and the longer hose is ok (and doesn't rub on the prop shaft)?

Our 2005's intake strainer is mounted on the aft berth bulkhead in the engine compartment. It is just above the stuffing box and next to the water/fuel separator.

The valve and a female hose fitting (In which I screw in a   plug when not in use- for backup safety should there be an issue with the ball valve below it)  at the bottom of the picture was added by the PO. It's a useful freshwater flush  feature. When the boat is on the hard, I place a bucket of fresh water on the after berth. I have a 4-foot length of garden hose. The female end is screwed into a male connector just above the ball valve. The other end of the hose is placed in the bucket. The engine water intake is closed, and the yellow handled ball valve is opened, allowing cooling water to be drawn from the bucket . After I flush everything, I wait until the bucket is sucked dry and then I pour in a few of gallons of antifreeze and draw that through the HX and muffler to winterize. When completed, I close the ball valve and open the raw water intake valve to drain any remaining water. It makes winterizing the engine easy.

 Our raw water intake valve is located beneath the aft berth. It has a convenient access door just as you enter the aft cabin.
 

For some reason, I'm having difficulty posting the photo of our strainer set up. I'll try reformatting

OK. Maybe the 5th attempt to send this will be a charm. I have a Macbook Pro laptop. The Apple photo format appears to be unfriendly to this web site. I don't want to go to a free web site to convert the photo to a friendly format like a JPEG file for fear  of being hacked. So, this final attempt includes opening the photo in the "Preview" app, reducing the file size to 1.7MB, copying the image and pasting it into a Microsoft Docx file, and attaching to this post. Maybe our web site will be happy with this attempt. I hope so, because I think many would like to see the setup.

The black hose is  from the sea cock. Cooling water travels from this through the yellow handle ball valve into the strainer through the blue hose and proceeds through the strainer into green hose - all  drawn by the water pump. When the ball valve is closed, the strainer draws water from the garden hose placed in a bucket. The 4-5 feet of garden hose has a female connector that screws into the male connector on the ball valve. This normally has a plug screwed into it that I made from a female hose connector filled with red epoxy. Without the plug, if the ball valve handle was accidently moved, it would allow seawater to flow into the boat when the sea cock is opened. The  hose that hangs in the bucket has no need for a connector on the bucket end, but does have a couple holes drilled in it. The holes prevent suction from sticking the hose to the bottom of the bucket and starving the engine of cooling water. 

 The hose used to fill the bucket has an  adjustable nozzle so I can match the water draw rate  and keep the bucket at a steady water level. If I  hooked the feed hose directly to the ball valve connector, I wouldn't be able judge the flow and would risk blowing the water pump or HX seals.