I've been thinking about the Shredder and how he'll be portrayed.
If they do make him Colonel Schrader, I think it could work if they made him the Ultrom Shredder, Ch'rell from the 2003 series.
In that series, he had come to earth many years ago and, using an organic suit similar to Kraang's in the 80s series, assumed the identity of Oroku Saki and, based on a japanese legend, became The Shredder.
He later murdered Yamato Yoshi for information related to TCRI.
If they were to use this incarnation and his backstory, they could say Kraang sent Ch'rell (or perhaps an amalgam of the 2 went) to earth to plan for (like in the original script) the arrival of the technodrome from dimension X and that, to aid in his efforts, he assumed the identity of people on earth including Oroku Saki (murdering Yamato in the process as well as utilising the foot) and General Schrader to gain access to government resources in order to (like in the original script) build a portal to bring the technodrome and soldiers to our world.