There's two questions you have to answer, that determine what rules you get (and, regardless, will disfavor some techniques and methods):
How safe should it be?
Every sport outlaws eye gouges, groin strikes and throat strikes, as these end matches, and can potentially permanently disable or kill your competitors.
After that, though, the question is how much do you want to risk your people? Many places outlaw elbows or knees to the head, however, these are among the most powerful tools any striking art can bring. What about attacks like foot stomps or shots to the back of the hands? Both of those could break something and end a match quickly.
Are gloves required? If so, how heavy of gloves? Part of what changes what punches and strikes work, is the types of gloves you wear. Gloves stop people from breaking their hands, and that in turn also dictates what targets are viable.
What counts as grappling and when do you stop it?
You mentioned your main goal is to avoid ground fighting. Ok, is a standing clinch acceptable? Is it acceptable for a short period? How long?
How about a neck grab in order to deliver an elbow, a headbutt, or a knee? What about standing throws? A standing choke?
Can you grab a kick that missed and hold onto their foot? Can you do that if they leave a punch out too long? (also presumably we're outlawing moves that tear tendons or break bones directly)
If one person is tripped or thrown down, is there any scoring penalty? If not, people won't bother throwing. If there is, how much of a penalty is it, since you wanted to focus on standing striking and not a throw-down match?
The divide between grappling and striking has never existed in actual combat - you use anything that works, and the usual question of what to focus on depended mostly on your weapons and the armor involved.
As you go more towards sport, you have to ask what kind of safety you're looking for and what constitutes an entertaining enough match. The rules you create end up having a few optimal methods by the limitation process itself. There's no one set of rules, which is why even in combat sports you see a good amount of variation in the tactics and choices people make, and places where certain arts do better than others.