the signature vs plat issue is only for personal cards.
For business cards, there is no such risk. Opening the CD for $1500 for the business (some people may get approved without! But most apparently are not) is sufficient to get the bonus and also use the card a little bit.
If you plan on putting a lot more on the card for some reason, put more into the CD.
Eventually the card can graduate to an unsecured one if you've been good.