I guess it makes sense making use of the built-in brand awareness - globally - of HBO, rather than starting from scratch.
From a non-US perspective, it'll be a straightforward value proposition - depending on how they price it.
Of note, HBO doesn't operate everywhere already. For example in the UK, they did a massive deal with Sky - so everything HBO comes to us via the Sky platform with a handful of exceptions where HBO had another UK co-producer. But that Sky deal will be up in the not too distant future, and that'll be when HBO Max launches. As it happens, Disney also did a massive deal with Sky, and their agreement comes to an end very soon. So Disney+ won't launch in the UK until they've disentangled themselves from Sky.
I do confess that from a US perspective, you end up with a complicated mix of HBO Go, HBO Now and HBO Max which could be quite bewildering to the average consumer. But I suppose that's WarnerMedia desperate to hang onto those hefty cable TV revenues for as long as humanly possible before they have to chase streaming dollars. But if HBO Now is already $15 - a few dollars more than Netflix - then it's hard to see how HBO Max can charge more than a tiny bit more than that for all their other stuff. Not with Netflix at $9-13 (for non 4K) and Disney+ at $7.
The smart move is to surely "upgrade" HBO Now subscribers to the full HBO Max for a year or so, and then start ratcheting price difference later. Separately, they need to offer HBO Go subscribers some kind of cheap deal to get them all the HBO Max extra stuff, I assume without losing the good will every cable operator.
In the UK, I would expect HBO Max to launch at a price on a par with Netflix in the UK (£6-£9 for non 4K). It's far easier to drive people in early with low prices, and slowly increase them later.
Adam