Everything you describe sounds like China in 1980. They designated Shenzhen as a special economic zone and it became a model for the rest of the country. Whether or not Belarus benefits in the long run, who knows, but it's a good deal for China.

The EU sanctions expire in a few months, and currently only target individuals and companies, there is no general trade embargo so access to EU markets should be fine. Also China and the US are outside every single European institution but there is plenty of trade.

http://www.reuters.com/article/2012/10/15/belarus-eu-sanctio...

Being landlocked won't be an issue for exporting finished goods to the EU, but perhaps there will be an issue for raw materials and component supplies.