1. By gods do you mean Shards? or the Returned? Because the whole spren Nahel bond thing that powers the magic on Roshar is used by everybody on Roshar that uses magic...
Edit: 3. Oathgates are teleportation on Roshar, and we have Elsecallers with teleportation. We don't need more teleportation.
4. do you mean that some property of the Parshendi (maybe a special form) allowed them to call lesser voidspren to make Shardplate? How are parshendi fabrials? also, doesn't shardplate have gemstones in it?
Edit 2: I apologize if this seems rude, I am just curious as to how you drew these conclusions