Whether this deal would be ok for the Cowboys or not depends on the parameters of the deal. A second plus a contract is too high.
What is ET at this stage of his career? I'm not sure. If the Cowboys asked for permission to speak with his agent, then the Cowboys probably believe he has something left in the tank. Otherwise why bother?
Can he play out a 3 year deal at a high level? Maybe but there's no guaranteee. There's risk involved in this.
You can't evaluate this potential deal as to what what ET has done. You have to ask what will he do going forward. His best years are likely behind him.
In terms of pure compensation a 3rd is rich to pay. A 4th is about right. Anything less is probably in the Cowboys favor.
But what about the contract. Does ET want to play for the Cowboys (probably does) and if so will he do it for a reasonable deal?
I wouldn't pay top 5 money for ET because he won't average out as a top 5 safety for the rest of his career. Even top 10 is dicey because he could fall off a cliff and he has been injured of late if I remember correctly.
The draft pick compensation is probably an issue but the elephant in the room is probably the contract numbers.
If ET would play for 3 years at 10 million per year for a 3rd round pick to the Seahawks I think he would be a Cowboy. Anything more than that on any part of the deal will probably kill it. Even that cap number might be a little too rich for the Cowboys. He's not ET in his prime.