Okay, memory not being perfect, there's one other possibility. It's possible, though I'm not sure now, that when the server park thing was first talked about, Anet said you couldn't play on another server at all, if you were in Europe. It MIGHT not have been about guesting. I remember this big huge fight about people not being able to play with their friends a couple of years ago. I'm not sure now if it's guesting that was being discussed or being able to play at all by choosing a server outside your server park. I'm still pretty sure it was about guesting though, but I'm looking for the posts from back them and I'm having trouble finding them as well.
Edit: It also may be hard to find because guesting wasn't originally called guesting. They called it something else when they talked about it before the term guesting came into view, but I don't remember what that was. I do remember when they started calling it guesting though.
Yes, it would cost a lot of money to do it, now. Back when they were designing the system I imagine it would have been quite advantages and cost-friendly to base it around cross-server guesting. Also, where are you getting the information about their technology being all new and never used before?
I understand your frustration, I thought we'd be able to guest over to EU servers too. I mean, we can transfer to them so you'd think it'd be fine. But the problem with computer code is that it's never straightforward. I'm assuming(which before anyone says anything because this is my own speculation) is that they originally intended it when creating the feature. But once they had it working they encountered the latency problems. From there, it was probably deemed not worth the money to upgrade after that.
I mean it could even be something as extreme as, they'd have to scrap the feature and completely redo it from the ground up to fix. We just have no info and they're obviously not going to release it since this is the only MMO doing it on such a massive scale and is completely in each players power to control.
Considering that they're not charging us anything to play the game, it's not entirely unreasonable. It definitely sucks, it's definitely a let-down, but it is what it is. If I had to choose between not having it and being able to transfer for free at any time versus having it and only being able to guest in NA, I'd probably still choose guesting over free transfers.
I'm glad that this feature is finally coming. Not because of the guesting itself, as this is a feature I'm unlikely to use. But the closure of the free world transfers that'll come along with it, will hopefully lead to a situation where the position in the WvW ranking will finally represent the actual strength of the servers. No more whole WvW communities abandoning their T1-3 servers to join a lowranked realm because of too long queues. That's really good news for midlvl servers like mine that got steamrolled by suddenly vastly superior enemys coming from the nirvana of the rankings.
I'm really looking forward to better balanced clashes in future.