Among other concerns,
- They have had erratic fluctuations in quality which has been disappointing for longer in history than it's been good.
- You could say they took the soul out of Citroen when PSA was founded turning them into badge jobs (although the DS line has reversed some of that).
- I really don't see the synergy between the brands, they don't have a similar ethos to Opel/Vauxhall which seems to be more aligned with German sensibilities.
- There's no guarantee they won't just shut the operation down and use the manufacturing capacity for themselves seeing as GM lost money on these marques for over a decade.
- They bought and retired many UK marques when they took over Chrysler Europe.
- Depending on which way the French elections go a protectionist government may seek to make things difficult for PSA which Vauxhall would likely suffer from.
If VW didn't already own Skoda I would have thought that would be a good pairing (emissions scandal aside).
Sorry, missed this last time (for whatever reason, it's not notifying me when you post).
Some valid concerns there (as well as some we've already been over). I still think the quality thing is a moot point given Opel/Vauxhall is hardly an industry standard bearer in that regard, and the soulless Citroen thing seems more or less irrelevant to the discussion seeing as that company continued producing "proper" Citroens long after PSA was formed in 1974 (just off the top of my head: Visa, BX, CX, XM, Xantia, C6, and most recently the DS models and the C3/C4 Cactus).
What it actually did was made Citroen profitable, which is something it always struggled with when it was being really wacky and focused on engineering at all costs (similar to pre-Fiat Lancia).
Brand synergy is a fair point, but one that again is open to movement when the company hasn't made a profit for the best part of two decades. There wasn't a great deal of brand synergy between Renault and Nissan either but when Ghosn stepped in he made Nissan profitable within the space of twelve months and the brand has subsequently produced cars like the 350/370Z and the R35 GT-R, so it hardly sounded the death knell for Nissan.
Shutting down the operation? A risk, but if that is the case then it's one Opel and Vauxhall has brought upon itself by producing uncompetitive products for far too long. And if they do use the manufacturing capacity then that's hardly disastrous, as it will at least maintain some jobs.
However, this isn't like Scion being shut down. Opel/Vauxhall doesn't just rebadge an existing manufacturer's products (for the most part), it makes a wide range of vehicles unique to those two brands. The risk of the brands simply being phased out is low because there's presumably massive equity in the products they already produce, the R&D, the factories, the employees etc.
And as you note, VW already has enough on its plate. It's struggling to make SEAT justify its own existence and has had to slash all its motorsport programs to prepare for the Dieselgate costs, so I doubt VW will be in a position to buy any more brands for quite some time.
I'm not sure how it'd be any better than PSA though - VW Group would have had no more use for say, a Corsa in a market where it already sells a Polo, A1, Fabia and Ibiza to different audiences, than Peugeot does when it's selling a 208, DS3 and C3. Even if a Corsa or Astra became just a Polo or Golf underneath, who would you sell it to without taking sales from the four existing alternatives that already occupy every strata of the market?