That's a shame.
However, to describe the Culture as 'benevolent' may be missing the point. The Culture was an AI-controlled civilisation that, when it encountered another civilisation, basically said 'Join us or vanish,' then sent in Special Circumstances to make sure it happened.
Just look at what knife missiles can do; Horza described them as a 'semi-intelligent flesh slicer.'
Having said that, Horza wasn't exactly a nice guy, (but he wasn't meant to be)
If it is made though - look at the concepts and visuals.
GSVs don't look like ships of any known kind; a collection of plates and environs linked by fields. The same for Orbitals; although they are more like Ringworlds. The Worldships could be a sight to see
In 'Consider Phlebas', the Idiran ship was destroyed by a Culture warship hiding inside the sun.
The Culture could make nuclear bombs smaller than a human hair.
Well, estates are never a good thing when it comes to artistic legacy ... on the matter of the Culture, it would indeed be interesting to see whether SFX and SFX creators would be able to successfully visualise the extremely advanced hardware, and the ultimate futility of human existence in the company of far superior(?) artificial intellects. Iain M Banks touched on this here and there, but I feel he never had a chance to fully explore that aspect of the Culture.
The Culture is benevolent in the sense that it looks after all its citizens interests and rights. Those that threaten those interests from outside are dealt with by Special Circumstances. How those interests and rights are defined are of course as always the domain of politics.
Because we live in a culture where are conflict and adventure are exciting and interesting, and frankly I think humans always will, our fiction tends to focus on the periphery and how we deal with conflict and change, especially hypocrisy and heroism.
Most people in the Culture live extremely pleasant lives. And by most I mean 99.9%. when we managed to get our current culture on earth to 99.9% extremely pleasant, then we also could view it as benevolent.
The most excellent comparison to make is with Neal Asher's Polity. It's just a slight shift but the polity AI doesn't feel quite so benevolent, however I suspect for most citizens in the Polity, it's ok.
Sarah Newton in the mindjammer setting also created an interesting galactic culture called the Commonwealth. Pretty pleasant but interestingly continues to resist the growth of sentient AI. It would be great if anybody wanted to make a TV show from Mindjammer.
No spoilers please. It's the spoilers that make the exciting books!
The Polity AIs are more obviously darker than the Culture AIs, but probably only so because Asher gives us a proper glimpse behind the curtain with the Transformation series. Penny Royal, for example, is extremely complex, dark and dangerous. Asher shows the conflict and different views of the AIs.
Banks hints at it as well, but never front and centre.
I seem to recall that Ken MacLeod is one of the people involved with the estate, as Banks trusted him to make sure that his works retained their integrity. I may be wrong there, he may have just been involved in tidying up some of the edits from the work.
An opportunity to delve on screen into the multi book saga of Ian M. Banks, and, yet, sadly, Amazon, the multi billion Dollar corporation could not agree with the estate (just pay them a lot) and gift us this. :-(
I have mixed feelings about this, since the Culture is one of my favourite series of science fiction books. So many ways a TV series could have been a disappointment, but yet, if they got it right... Several of the books (Use of Weapons & Surface Detail spring to mind) would have been particularly difficult to convert, and there are numerous examples of characters both meat and machine who might (ultimately) be difficult to portray sympathetically. Some of the long (important and engaging on paper) exchanges between groups of minds would also have been a challenge on film.
A Culture (or Culture influenced) RPG would be cool - though I wonder how it could (or if it should even attempt to) handle the "scale" differences between minds (+drones), droids and meat. Heroquest's freeform abilities and masteries might do the trick, but some form of troupe play might be needed to allow a mix of different "scale" between protagonists in the same story - almost like a far future Ars Magica type of thing.
I love the Polity books.
I love the Culture books.
There is an arc in Polity, and a persistent hero.
They are complementary not overlapping.
The Straw Dogs RPG group often found themselves in Culture crossovers using BRP, see @Loz for details.
I do recommend the Mindjammer novel as another example.
We've successfully gamed as Ships and Avatars using Mythras on a few occasions. There's something especially satisfying about having your Combat Style listed as 'Murderer Class Fast Picket 85%', and your weapons list including CREWS, Effectors, and Focused Displacement Fields. Measuring your movement rate in Kilo-Lights is also pretty groovy...
And nova-level Gridfire and CAM dusting .... don't forget them!
It's because of the freedom of things like glanding and the myriad things that drones and various effectors can do is why I'd be tempted to use FATE or Mindjammer; so that, for example, getting into a game of Stricken, you could spend a Fate point to gland Sharp Blue to get a +2 Aspect on your rolls
For Singularities, I've followed the lead in Sufficiently Advanced. Tech is treated as a power attribute with traits underneath it. Nanotech would be base, with abilities underneath. Tech also has a scale rating depending how advanced.