Just a bit of info here. My engineer is quite the purist and the line he likes to use on me quite often is always "Anything in the signal path affects the tone. The purest path is always the simplest path". His feeling is that if the Di is designed right in the first place, any FOH engineer will be able to deal with the output level of the DI. Sure, you can ask a sound guy "Is my DI level ok?. Do you need more, or less?", but if you never bring it up and just present him with a usable DI level in the first place, the issue should never really come up.
And yes, while we are talking about just a few bucks in components, keep in mind I'm not just buying a couple buck worth of parts, I'm buying everything in multiples of 100, sometimes more if it's a special order part. A few bucks here, a few bucks there, really starts adding up when you are talking about a product with hundreds of components. We are trying to get the price on this amp as low as we can, given the design and every little bit helps.
I am genuinely interested to see if this is a feature guys are actually using, or not. The couple times I was asked about my DI level and I told the sound person that I didn't have any way to control it, he was like "No problem". So, in my experience, it's never been a feature that seems overly useful, as I've never owned an amp that didn't have a usable DI level.
From the foh end of things, if you can guarantee that the level from the DI will be somewhere between the level of a vocal mic and the level of an FX return, then simpler is definitely better. I need clean signal a lot more than I need hot signal.