These kinds of ideas are clear to everyone who has thought about the topic. But if I can interject some personal experience ..
I've had an open source text up for more than a decade http://joshua.smcvt.edu/linearalgebra . It is easy to find; if you google "linear algebra" today then it is the third item. But although I have said on the page that I welcome contributions, I have had very few, and those few mostly bug reports-- which I am glad to get but they are not what I imagined I would get when I first put it up. (I will be putting it up soon in a public version control repository but let me note before I get emails that for most of the life of this project the best option really was to offer a .zip of the LaTeX source.)
The text if fine but I could in a minute list many shortcomings. For instance, it could use with a graphic designer, it could use with the skills of a person who can do illustrations, I would be delighted to get ways to interact with Sage, I would be glad to get tests from people who have taught the course, I would be glad to get help with e-readers (I don't own one myself). Etc.
I am currently doing an update that has taken my between-semesters break, and that threatens to spread into next semester. So offering such a thing is a lot of work. Some of it I am qualified to do but some of it I really am not. However, to this point, I have seen very little evidence that others will help so if it is to be done then I have to do it.
In short, more productive than listing the failings of others may be to pick a promising project of interest to you, and contribute a solution.
I've had an open source text up for more than a decade http://joshua.smcvt.edu/linearalgebra . It is easy to find; if you google "linear algebra" today then it is the third item. But although I have said on the page that I welcome contributions, I have had very few, and those few mostly bug reports-- which I am glad to get but they are not what I imagined I would get when I first put it up. (I will be putting it up soon in a public version control repository but let me note before I get emails that for most of the life of this project the best option really was to offer a .zip of the LaTeX source.)
The text if fine but I could in a minute list many shortcomings. For instance, it could use with a graphic designer, it could use with the skills of a person who can do illustrations, I would be delighted to get ways to interact with Sage, I would be glad to get tests from people who have taught the course, I would be glad to get help with e-readers (I don't own one myself). Etc.
I am currently doing an update that has taken my between-semesters break, and that threatens to spread into next semester. So offering such a thing is a lot of work. Some of it I am qualified to do but some of it I really am not. However, to this point, I have seen very little evidence that others will help so if it is to be done then I have to do it.
In short, more productive than listing the failings of others may be to pick a promising project of interest to you, and contribute a solution.