Don’t do it!
My outdoor cats cost me far more than my indoor cats. Between the fleas, ticks, and getting themselves killed, it’s horrid.
One of my outdoor cats is allergic to fleas. His skin and fur is falling out in patches. I can’t keep him in - he is a world class escape artist. Every time he gets out he brings a new flea load into the house, which he immediately spreads to all my indoor animals. He looks and feels horrid. He brings vermin in. Sometimes it’s dead, sometimes not. He brought in a dead rat once that my dog grabbed and ate, and she threw it up in my living room. Yuck.
My other outdoor cat got killed by a pit bull.
My indoor cat is sitting right now quietly on my lap. She has reached 17, and looks and feels nice.
Try and find a less stressful place to put the litterboxes. I love the tilty Omega Paws ones Amazon sells - I put them in the garage and find them much easier to use than the traditional ones. The motorized ones are a pain.
Our previous barn cat lived to 15 years. She was a ramblin’ wreck; lost her tale when it was stepped on by one of the horses. Her sister, also a smart huntress, only lasted 7 years. Both loved the life!
I suppose the easiest thing with regard to the litter is to finally and diligently saddle my son with this duty. During the fall, winter, spring months I basically work all the time (Barack’s New Economy). The box is neglected. It just needs to get done!
When I had cats (wife took them when she left), I had a motorized litterbox that sat on top of a cabinet. When it scooped, instead of going into the small container, it went into a continuous plastic bag. Could go about 2-3 weeks w/2 cats without emptying. It was great. Bought the setup on eBay.
I do miss the cats.
Your flea allergic cat is in poor health, which is why he attracted so many fleas. He needs high quality food or meat. Look for an expensive natural brand of cat food for that cat. You will see his coat improve and become shiny. Do not let him eat kibble - it’s poison. Junk food for cats. You can also rub garlic powder into his fur today to keep the fleas off temporarily.