I think this is the meat of the argument here:

Being trustworthy and acting with integrity should be his/her only function.

And to illustrate the point:

there is one witness who has been found to recklessly game the liquidity reward mechanism and derive very high profits at the expense of the network, which led core developers to removing liquidity incentives altogether. Is that a good example of integrity and trustworthiness? Can we trust this witness not to side with an attacker if this can net him a large profit? I for one would much rather have trusted community members regardless of their skill levels beyond the simple skills required to securely run a node.

We may be taking for granted that witnesses are honest and acting in integrity and ideology for the site, hence the title. Any witness NOT in accordance with this should be nixed. And I agree that mixing witnesses pay with development may be hazardous for this very reason.

HOWEVER, in @smooth's defense, many of the operations a witness manages in effort to protect the integrity of the site are also the qualities that make them witness-worthy. Meaning, we vote for witnesses because they are doing things like this. A lot of the "witness" functions are simply inseparable from the dev functions, at least at this early point in the game.

But in the end, I agree with @recursive. It may not be a good idea to mix witnesses with development. If witnesses are doing things to progress the platform full time, including donating their own money, perhaps they should be getting paid a lot more than $6,000 a month--but not as witnesses.

The problem is, who has spare time to be a volunteer witness with all of the projects they're running?

Sure, it's an honor. Bla bla bla. But when it comes down to it, if these witnesses are getting nothing for running a node, then that node should be a pretty simple thing to run. Or we're taking the WITNESS for granted. They have a lot of work to do, and they have influence with which to do it. This needs to be rewarded.