I really don't have the time needed to read all of 12 pages so maybe someone has already wrote that... but i have something do add.
1. Spren can be killed (i think) - didn't Kaladin using Syl killed one of the voidspren in kholinar? i read only polish version but i think syl asked "did we just killed this spren?" - i don't think that this one particular voidspren have turned deadeyedvoidspren (!) or something, it just got KILLED (of course it was syl who killed it, not like breaking an oath).
2. remember Warbreaker? remember Nightblood? i must ask... did anyone have nahel bond with it? or you just need to hold it to hear it? there was another blade - i don't know her name in english version (polish = Lazur) warrior women who commanded soldiers of the wall in kholinar. one of the honorsprens on the boat in shadesmar said something like "it speaks!" - does she had nahel bond? this can be just it - that Maya is regaining her mind - without the nahel bond. you can see that many many spren in shadesmar have minds - without any bonds. can Maya become a spren with mind that works, but without any bond? and due to adolin's connection she can WILLINGLY change herself to a sword? like Syl can be a girl in dress, can be a girl in havah or be just a cloud. or a sword