I am an attorney, maybe the only one around here, I'm not sure.
My advice is to go with an existing license. If you guys want something more specific, figure out why you might want it that way, decide how important it is, then just get over it.
Sorry if that sounds rude, but you are a fool if you try to write your own. I'm not this impolite, in general, but when I go into attorney mode I think it best to be smack in the mouth blunt.
The reason existing licenses are so convoluted and hard to understand is that they are full of what I like to call "magic words". These are words of power. Words that have been raked over time and again by various courts and authorities. Their meanings are paragraphs long, with case histories and definitions vetted at the highest levels.
If you write your own it WILL NOT mean what you think it means when a court of law is done dissecting it. Even a native speaker will not write one correctly. You need someone that knows the correct phrasing. Phrasing that will hold up in court. That person will cost you money. I assume that since you are coming on here asking for advice you don't have that money.
It'd be a waste to hire a lawyer anyway, he'd spend his time convincing you to go a standard route. Then, if you disagreed, he'd be more than happy to paste you together a convoluted license that STILL no one would understand, but might hold up in court.
I don't even know how to do a license correctly, but I know enough to tell you without a doubt that you should not do your own. The end result will be nonstandard, hard to understand, might chill creativity and distribution and ultimately it won't hold up in court the way you think it will.
International intellectual property law is the specialty you are looking for. For reference I did low level family and criminal law. Very low level.