I know that there are a number of commercial ECU tunes available:
EPL
GIAC
APR etc...

But was wondering if anyone here has done work on the newer 3.0T engine to get something equivalent to a stage 1 tune? TIA

not entirely sure, but are you referring to the cable per se? If so, then a Ross-Tech VCDS, but I'm open to suggestions.

I know the forum has been largely dedicated to older ECUs and hence why I posed the question about newer ones and what others have done and how.

something like http://byteshooter.de/ or will kess v2 work?

Chinese shit won't work.

Also, the gearbox needs doing on every single one of these. That means GS19 for Simos 8.3, DL501 gen1 for Simos 8.4, DL501 gen1 or gen2 for Simos 8.5.

I have done all of these. 8.3, 8.4, 8.5 and the respective gearboxes. Have dyno graphs to show for every combination and so on.
But if you don't have a proper tool to write them, then you are just wasting time with these questions, so it is irrelevant what I or someone else can or can't do.

AFAIK:
Byteshooter will do only up to 8.4 in boot and it won't do DL501 Gen2. It will do GS19 with the right module.
CMD is the only tool that does 8.5, but does not to DL501 gen2 or GS19.
X17 does up to Simos 8.4, it also does both EEPROM variations of 8.3 unlike many other tools. It also does GS19, DL501 Gen1 and DL501 Gen2.

So there is no single tool that can do all combinations.
I use CMD and X17 to do all variations, and the cost for those tools is about 10 000 EUR.

The price I usually charge for Stage 2 (incl. pulley and installation) is around 1000 EUR.
It is much cheaper to go to a tuner and get it done than buying the tools needed. Just have to find one you can trust.

I would recommend UM.