Are your "major" flights in paid F or C? If not, is an upgrade something you need or seek? Are there airlines you won't or prefer not to fly on? What other destinations do you fly?

The Alaska Airlines Visa might do you well, with the AS Mileage Plan for your accumulation. You earn miles on most OneWorld carriers as well as NW and CO - and many count for qualifying miles. The 50K on other carriers will qualify you for AS top status. You don't get a lot of benefits as an MVP Gold flying the other carriers, but you do get some.

I use the AS Visa as my primary business card. I don't know the reasoning behind your attorney's advice if you keep all the charges segregated. But I am not second-guessing him, nor giving you advice. What I will say is that I'm an attorney that has used a "personal" Alaska Airlines Visa as my exclusive business card for about a decade, without issue (well, issue other than with the bank...)