Any tips or advice to make sure a CoC request is approved?
The critical is to make sure you have a ready back-up plan. While the policy changed and supposedly you can stay around during the review for maybe 1 month? if one decides to pull COC needs to be ready to walk and hopefully switch employer on the spot.
At that point it is a risk profile if you actually get the money and play the percentages. If you also time it after the bonus period you may get ahead of the VSP crowd. Possible you will be entitled then to another annual bonus at guaranteed percentage/target.
Having a good lawyer in place will help. Pay couple of thousand for retention fee and ask specifics for your case. Simple search for Houston lawyer, employment law and COC will bring a list. There are actually lawyers that teach this stuff in college locally.