Can I update my MSc thesis after submission Due to events beyond my control I couldn't finish the writing as planned. Most of the thesis were rather ready and not to bad (if I might say) but I didn't finish all chapters well, there are some logical gaps and moreover some of the rather central diagrams were not clear at all. In normal circumstances this could be fixed in a few days, but in this case there were no way to do it. 

I couldn't postpone to submit the MSc thesis (due to maximum time allowed) so I just quickly wrapped it up (removing comments in text and tried to cover some logic steps in sloppy sentences etc). 

Now, the thesis are to be archived and moreover, some colleagues from other universities want to read it. It's a rather big interest, but I'm embarrassed about the missing parts and even some typos. Would it be immoral to correct the errors and fix the missing parts to create a better, more readable study, if I clearly state that it is an updated version? Could I call it a report based on my thesis or something like that? 

What would be the best way to deal with it? I'd love to produce a well written document at the end, but shouldn't hide the problems of the original, submitted thesis. I have no intention of hiding the original thesis, but the results would be much clearer with n update.
There is nothing immoral about correcting mistakes in your earlier work. Passing off your amended version as that which you submitted to your institution would be rather questionable, though.

I do not think that any library would replace your original submission with an amended version unless that amended version was created through an official process at your institution. I don't think that such an amendment process is available in most cases for an MSc thesis. 

So your problem of trying to drive readers towards your updated, amended and corrected work, remains.

Perhaps one solution would be to correct your original work and have a version of this available online, with some appropriate title which indicates it is an updated version of your earlier work, as you suggest. I suggest that you make it very clear where your corrections were made in your updated version -- going so far as to quote the original work and indicate what you changed and why.

You can then point your colleagues towards this updated work. 

You original work will remain on record, and any failings in it will be reflected in the grade you receive for it.