You have one little problem...It's a little fryer!
The thing is that home fryers are simply not big enough to use commercial methods. The fat volume is to small to hold heat when food is added. It cools down so fast...What does it hold? 3.5 to 4 litres? So adding say a 400 grams of fish (fillet with batter) is adding 10% of cold to hot. That would be like adding a 3 kilo fillet to a commercial fryer...It would not work!
Your idea of using foil will not work, sorry. Sure, it will catch the batter, but it will stop the proper "cool zone flow". Effectively the fat above the foil will not be hot enough.
I understand your desire to make it easy and safe. But, some things just need work and care...
This is what I do...I use my wok to "blanch" any battered and crumbed food. This has a number of advantages. First of course, the batter or crumbs are sealed and so wont stick to anything in the fryer. Second is that the fryer fat will stay cleaner and fresher for much longer. So, you actaully reduce the cost and work because the fryer needs less cleaning and fat changing!
I use 1 kilo (about 2 lb) of vegetable frying compound in my wok. I find that that is a good amount. I use a steel bowl and sieve to clean the wok fat when ever it needs it. Simply put the sieve in the bowl and pour the hot (or warm) fat in...Leave it in the bowl until next time.
Of course, another option is to visit the frozen section in your local grocery store...These days, if it's fry-able, it's frozen!
I hope that is of help.