Beer and urinal goes together. A urinal in a mans cave is an excellent idea. Keep the toilet facilities that way there won't be any accidents in the other bathrooms.

1. Look up the health department rules on septic systems for your state. Get a state certified septic designer to look at your site and come up with a fix for your wastewater treatment system. I know this is a big expense and you would like to postpone it. However the rules are revised periodically, and everytime they are revised it gets more difficult and expensive to meet the standards.

2. While you are getting the septic problems fixed, look at getting a small lift station with a grinder pump to handle the wastewater from your basement. The grinder pump would take the waste water from your basement and convey it to the septic tank for the first step in a series of biological wastewater treatment steps. This isn’t cheap either, but the lift station with grinder pump is a more durable solution than those household systems that tend to clog and breakdown. The septic designer should be able to help you with the lift station and grinder pump design, since many septic systems involve pumping to an up-gradient treatment system. The septic system designer might be a different person than the septic system installer. Not everyone has the licenses and equipment to do both jobs.

3. For me, the basement powder room would be a quality of life issue. Keeping those men in the basement and out of my other bathrooms and the rest of my home would improve MY quality of life.

I'm a guy, and I think a urinal is a great idea. I think more homes should have them (with toilets in the same room). In your instance, it would meet 90%+ of the needs of the dwellers of the man cave.

And, yes, dealing with the septic is a prime issue.