I was thinking of something similar since every dog park in my area is lacking some feature. Either they are in a wonderful area, but not fenced, or they are fenced and even have some agility obstacles but completely with concrete (wtf, really?)...
I personally would NOT sell alcohol and even forbid the use of it completely. Thinking that intoxicated dog owners (or worse: people not really familiar with dogs and dog language) run around there is horrifying for me.
I would set up some cafe area where people can meet after/ before/ between the play times but with having their dogs on leash there, for 2 reasons:
there's hardly anything that annoys me more when visiting my local dog park when other owners just stand there drinking coffe to go form the nearby bakery with other dog owners or just sitting on a bench and checking their phone while drinking coffee and not giving a rats ass about what their dogs are doing.
dogs might get hurt from hot drinks when they spill.
I'd set up different areas/ projects:
1 big green for playtime for bigger dogs and 1 for smaller breeds
some small parcels where people can meet up with friends of them for some more "private" playtime for dogs that are dog selective but would love to play with their friends without the level of stress for their owners to constantly check who's entering the park and what dog is approaching their dog)
a complete agility field that is open to visit once a week for people to get to know it but has to be booked for a small fee the rest of the time. Also: coop with local dog schools so trainers can introduce their agility course, give people who are interested in agility some first info. People then can decide if they will just visit their agility cparcel for some fun play every now and then or use the dog schools agility course to do it more "seriously"
pool/ swimming area
coop with a local dog trainer(s) and vets for an open, weekly consultation hour people can use if they are looking for "smaller" advice and maybe just have some general question they wanna discuss with a professional but do not think that they need to actively ask help for. Vets and trainers could advertise their services, show people how they work and give them the chance to meet them in person.
coop with local barf-shops, offering some kind of "diner for dogs" once a month, advertising their services and give people advice and consultation about dog diets.
indoor play area for rainy days/ winter
1 puppy only day, also in coop with local dog schools
have a small shop where I sell high quality food and giving people/ customers the opportunity to organize centralized buying (to not worry about minimum order value and to get discounts when buying stuff from the internet) and also give them an "adress" where they can pick stuff up so they do not have to worry that their frozen BARF stuff will lie in some postal office when they do not have the opportunity to pick it up in time because of work.
in the long run: doggy day care/ pension, but only for a small amount of dogs to keep a high quality standard (and not just put them away in crates).
building some kind of community, like: people who volunteer once or twice a month to help cleaning up the place, repair obstacles or maybe offer some other kind of "community service" (like organizing a visit at the beach for/ with other owners) will get some discount of whatever fee I would have set in place.
maybe some kids stuff: like having a course for kids to obtain some kind of "dog driving license", where kids learn how to properly behave around a dog, which dos and donts to follow when walking the dog and how to react in maybe dangerous situations (as a side note I really can't count the times where I've seen kids walking the family dog and doing everything wrong) or coop with local kindergartens and dog trainers to teach kids how to behave around a dog.
maybe some special day and coop with local retirement homes. Elderly people can have a fun day outside of their home and play with dogs and service dogs (or service dogs in training)
This basically is what I dream of but I doubt I ever will make this happen. Maybe when I'm retired.