Word for person willing to argue contradictory things depending on what suits him

Is there an adjective or a noun to describe a person willing to argue contradictory things depending on what suits him?

For example:

"Our company should buy X — it's good for the shareholders". Realizing later that it's bad for his career: "Our company should not buy X — we have too much invested in Y".

Solution 1:

You could call someone like this expedient (World English Dictionary: "inclined towards methods or means that are advantageous rather than fair or just") or maybe a vacillator, someone who "fluctuate[s] in one's opinions" (WED).

Solution 2:

One role that fits your description is lawyer. That category of person is routinely called upon (and answers the call) to argue differing points of view, some of which are wholly inconsistent.

They also regularly take multiple, sometimes contradictory, positions within the same legal brief, referred to as "arguing in the alternative" in which they are, in effect saying,

If you don't accept that explanation, what about x [an alternate explanation]?

They are often called advocates because they advocate for a client's point of view, regardless of their own position or belief (or the position or belief of one of their other clients).

If the person lacks admission to the bar, you might just call them inconsistent.

Solution 3:

If somebody always argues on the opposite side of an issue than you are arguing, I'd call them a contrarian.

Merriam-Webster: a person who takes a contrary position or attitude.

If somebody is willing to argue on either side of an issue, depending on which one is in their best interests at the time, I'd call them a hypocrite.

Merriam-Webster: (2) a person who acts in contradiction to his or her stated beliefs or feelings.