Wow - the topic hit me like a ton of bricks. I helped my father write the nusach for my mother's matzeiva. He wanted it to be in an acrostic style. He wrote the initial text, and I helped edit it. When he was niftar I remembered the love and care he put into getting it right for my mother, and wrote an acrostic for him (with the help of his siblings and other relatives).... and I also was asked to help with my great-uncle's matzeiva by his children (they are not at all frum, and their father was more traditional).
Of course, after writing those, I thought about my own ultimate return to Olam Ha'emes (which I"H will not be for many more years!) and short of leaving instructions to minimize the language - i.e. name, abbreviations, and not much else - I think it's a bit arrogant.
For example, I had a relative who said no hespedim at his leviah. Which was honored by his family. I think that's okay - but very different than writing your own hesped and asking it to be read at the funeral.