My thoughts on outhouses:
I used an outhouse until I was 14. Lots of experience.
There are many good outhouse building ideas on the internet. They will give the basics. Here are some additions I would suggest, as time and money permit:
1. Put a solar powered exhaust fan on the vent pipe.
2. Insulate the outhouse with foam board. Including the door, roof, and floor. This is as much for wind resistance as conserving heat, but that does help.
3. Consider solar charged automatic lights outside of the house and of the outhouse, and inside of the outhouse so you can see the outhouse as you approach just in case of animals, and inside so you do not have to fumble with flashlights on dark days and at night.
4. Being chilled is not conducive to regularity. I highly recommend a tent-safe heater such as one of the Buddy Heaters. Especially one that will allow use of an external tank. And one that is very easy to start with a pizeo igniter. (The insulation is very important if you do add a heater.
5. In the summer time you can keep sanitizing wipes on a shelf in the outhouse. In the winter time they get very cold out there. Best to have them, along with a flashlight or headlight (even if you have automatic lights), and an extra roll of toilet paper by the house door you use to get to the outhouse. Despite best efforts, if you do not take paper with you every time, you will wind up without any when you need it at some point.
6. Keep an extra roll of emergency use only toilet paper in a closed metal container. Make sure everyone understands that if it is ever used, a new roll is to be put in as soon as the person gets back to the house. Not later. Not when it warms up. Not when the next person goes. Does not matter if there is still 99% of the roll left. The emergency roll goes on the dispenser and a new roll goes into the container.
7. The same thing goes for feminine hygiene items, whether or not there is anyone in the home that needs them. You will eventually have a woman that is going to need them, and unless she is familiar with the rural outdoor plumbing lifestyle, will not have what she needs.
8. While I did not see it in the instructions, and I might just have missed it, make sure the interior of the outhouse is easy to clean. And keep at least some cleaners there, in a locked cabinet if there are children around. It is even more likely for people to not make it quite in time to the outhouse than at a regular bathroom, since they tend to put off going until it is critical. If they do make a mess, having the things to clean it up with right there make it easier, more likely to be done, and rather less embarrassing. In the same vein, it might not be a bad idea to keep a pair or two of different size coveralls so a person has something to put on if they do have a bad accident.
9. There is nothing wrong with prettying up both the inside and outside of an outhouse.
10. Consider a high quality skylight or a white fiberglass roofing panel to allow light in during the day. Daylight is a good sanitizer and odor eliminator, so it just might help some.
11. Make sure you have a good supply of cover material inside the outhouse, and plenty more handy to it. You will keep odors down significantly if you do cover each use with an absorbent. There are lots of options.
12. Put an easy to use lock on the door, preferably with an in-use indicator.
13. Do not be tempted to do a multi-seat outhouse. I know they were common at times, but modern society does not lend itself to them. The only reason I would is if the family is fairly large with several same sex children, especially teen girls. They will usually share a facility where individuals will not.
14. Do not skimp on the receiving hole. And, if you have the labor to dig one, try to get them to dig one or two more, cover them over, and keep the extra earth handy and covered to fill in the old one. Do not wait too long before the outhouse is moved. You do not want the waste closer that a foot to the surface of the ground when refilled, and two feet is much better.
15. When an outhouse hole is refilled, cover it with something that will keep a person from sinking into it. You step on a recently filled outhouse hole and you will sink, unless there is something over it. And mark it well.
16. Keep the in-use toilet paper in something that is mouse/rat proof.
17. If possible, have a separate urine collection system. This could be a bucket or other container with a tight lid and a hose going into it with a large funnel. Difficult for women to use, unless they use one of the stand up urine diverters that are available. An alternative is to have a second seat over a funnel like collector that drains to a container outside the outhouse. This would be much easier for youngsters and women to use.
Just my opinion.