Andy,
You have provided your fix in the last para of your discussion. If there are tenons on the ends of the raised tie they must be removed to avoid cutting into the plate/post connection. I suggest you leave them in place by cutting them off with a recip saw prepatory to raising the tie to it's new altitude. The strap and bolster/ships knee support for the ends of the raised tie bring it all together. How do you propose to fasten the raised tie end support elements to the post ?

You didn't mention any braces in this tie. If they exist will new longer braces be able to use existing pockets in the tie/post ?

work safe, have fun

deralte