Put a half-baked paper in arXiv for the purpose of documentation I'm sure this has been asked before, but I didn't find it.

I have been working on a side project for some time, but I don't have the time to make the final evaluations to make it into a peer-reviewed-worthy paper. However, I do think it has merit and I wouldn't want it going to waste.

Is publishing in arXiv for this purpose considered acceptable? 

Thank you.
ArXiv.org is a preprint server.  It is not intended for your purposes.  

Even though people do upload all kinds of documents (half baked ideas, their PhD thesis, lecture notes, ...), I personally think it inappropriate.

You might consider putting it on your website, or even emailing it to people who are likely to be interested.  Or, make time to finish it!