Since an optical kill switch caused interference, I do not use them anymore.
In all the regulations I do not see a requirement for an optical kill switch unless you plane weighs more then 55 lbs.

All you need is a battery cut off switch you can reach from the outside and some cut - off , which can be the throttle.
If anything else is needed, I'd rather use a choke servo which come in handy in setups where the choke is hard to reach.