Would it be considered as good practice to create a new Area51 proposal to poll for interest in reopening a StackExchange site that was closed during the beta?
If Go is a game, then why can't you make the Board Games site "a place that Go experts would gather"? The first step to achieving that status would be to start "posting very 'technical' Go questions".
This is not an unsolvable chicken-and-egg problem. You're the chicken, so all you have to do is lay a couple of golden eggs. And maybe tell your friends. Build that site the same way that you'd build the brand new beta site that you envision.
That seems like a better long-term strategy than creating your own Go-specific site that is all but doomed to failure, given historical evidence and by your own admission.
To me, this is a special case of the more general problem of creating a bunch of overly-specific Q&A sites, rather than just building up the community around the more general site. I don't understand why people resist turning the existing general site into a thriving community of experts on their niche interest. The site(s) can handle the traffic, and the tags make it easy to subdivide the content. You don't need a site specific to a particular board game, or computer architecture, or mobile phone platform, et cetera.
Any site that was closed during beta did so either because it didn't get enough traffic or because the site was misconceived in some way.
Unless you have a good plan for remedying what ailed it, trying to reopen it will at best lead to the same result. Now that the question requirements in the definition phase have been increased, it will be harder to get a previously failed site to that beta phase.
I think it would be better to go through the Area 51 process again for the topic. Instead of trying to revive a dead community its easier and hopefully more effective to start over. Many business ventures try and fail 2 or 3 times before finding the right mix for success.