Decided to replace the OAT Coolant in the 2014 Rapide S. The placement of the drain plug within the lower radiator supports creates a challenge to avoid spreading the dripping coolant everywhere.
After reviewing the similar issue on Aston 1936, I decided to adapt a plastic cap by making a hole and placing a 90d nipple to some surgical tubing and fitting the assembly on the drain plug outlet.
Regular hose was too stiff to make the turns and surgical hose would crease closed without the nipple.
Half a turn and a slight pull on the plug will allow for the coolant to flow within the drain line and not from around the plug. Took about 30 minutes to drain into a 2.5 gal. container with no leaks or cleanup.

Posting some photos of the drain plug and fitted improvised drain line. No need to remove the small front under tray but the belly pan has to be removed.
Not sure when Aston Martin switched to this style drain plug, but it should work for any model with the similar style plug.

 

I wish the coolant drain plug on my 2007 V8V was like that. It is the older style flat button shape with the only option being to unscrew until coolant starts to squirt out.
I drained / filled the coolant over the weekend.
I was able to catch about 90 % but the remaining 10 runs down the lower radiator support or dribbles everywhere

 

I would appreciate any advice on sizing the cap and surgical tubing diameters. My 2014 Vantage Roadster has the same coolant drain outlet and hardware obstacles.
Thanks

Edit: Taking another look at your solution, it seems that a tape measure of the outlet circumference will give me the cap or angled piece size I need, and the tubing size needed will follow.
FWIW I could not find any reference to this outlet in the 2010 workshop manual (don't have anything later) or on vendor parts diagrams.

 

I changed mine a couple of years ago, it's a 2015. I just put a large drain pan underneath and didn't really spill that much. I did not get nearly 2.5 gallons out of mine. Maybe a 1.5 gallons if I was lucky. I believe a lot stays up in the engine. Maybe I need to get the engine warm so the thermostat opens up.

 

My coolant change is due and I’ll be changing out the thermostat (47K miles)
as I’m starting to see a little delay getting up to the normal halfway mark. I picked up the Motorcraft equivalent thermostat with the improved gasket construction. Funny about the suboptimal draining given all the hoops we jump through to get the right coolant. I have used Motul Inugel but it’s no longer available in the US, and the Chevron Delo equivalent has also been hard to find. My plan is to drain and fill, get up to operating temp, repeat a few times.

As for the drain plug, it’s a pretty tight space and I did not find an elbow junction that would fit. Tomorrow I will get back under the car and remove the lower radiator brace out of the drain path. Looks straightforward based upon eyeballing and the Scuderia parts schematic.