As for optical kill switches, I had never used one till a couple of weeks ago on one of my 50cc planes when the throttle servo mounting broke pulling the throttle almost wide open regardless of the setting. This plane had a manual choke setup so that was no good either and with a 20oz tank my fingers were frozen almost solid before it finally ran out of gas. This particular plane is a very lightweight plane and with the 55 in it vertical is unlimited so that was a heck of a lot of plane to keep up with till it quit.

Now ALL of my gas planes will have an optical kill switch before ever being started again.

As for the advantages of a pull-pull setup, I see none what so ever on this plane.

For servo's, I run all 100oz digital metal geared servos from China which cost me $9.00 a piece and now with over 50 of them in various planes of mine and others in my club the only failure to date was a burnt servo on a choke due to being mis-adjusted and stalled with the choke closed. Otherwise I would look into something like Futaba 3305's, not digital but plenty strong. Futaba does not recommend them for airplanes but I have seen 100's of them over the years in planes and have used 30+ myself and never had a problem.

Ignition battery, I think your original 4500mah would be way overkill. I have never used more than a 2200 on any ignition and thats been plenty of battery for an entire day at the field. I do however run all my ignitions on a 5 volt regulator regardless of the battery be it a 5 cell NiMh or 2 cell Lipo. There are regulators out there that will provide a clean 5 volts at 3 amps and the cost/weight is nothing. Maybe overkill but I would rather spend a few dollars on a regulator rather than take my chances at have a fully peaked pack be jst a couple 10ths of a volt over the threashhold on an ignition then have to spend $50 for a new one plus loose a day of flying.