Honestly, these days I have no idea. When I said "wouldn't recommend" that wasn't an assertion to avoid; just a lack of opinion. Most of my recent experience is with Cloud vendors wherein the problem domain is quite different.

I've had experience with most of the big vendors and they've all had quirks etc. that you just have to deal with. Fundamentally it'll come down to a combination of price, support requirements, and internal competence with the kit. (Don't undermine the last item; it's far better if you can fix problems yourself.)

Personally I'd actually argue that most corporates could get by with a GNU/Linux VM (or two) for most of their routing and firewalling and it would absolutely be good enough; functionally you can do the same and more. That's not to say dedicated machines for the task aren't valuable but I'd say it's the exception rather than rule that you need ASICs and the like.

You can get exactly the same benefit by blocking non-established/non-related connections on your firewall. NAT does nothing to help security.

Edit: BTW--every time I see this response of "NAT can prevent external access", I severely question the poster's networking knowledge. Like to the level where I wonder how you manage to config a home router correctly. Or maybe it's the way home routers present the interface that leads people to believe the two functions are intertwined when they aren't.

Yeah, no. If remote hosts could not send traffic to hosts behind NAT almost nothing would work.

The hacks employed to make NAT work make security worse, not better.