I like the idea of the chain being a toggled block section.
In reality, it should ALWAYS be a block section, unless you have enough station blocks or other blocks to account for any trains in the system.
For safety's sake (and I know, this is just a video game, but I'm a full-time carny by trade, realism makes me happy), you never want to have fewer than one set of brakes separating any two trains in a system. In my coaster designing, I'm trying to go for as realistic a design as possible, and I think that as it stands now, the block system is pretty on point.
The only thing that I think bothers me about the blocks as they are currently is that the load block seems to take FOREVER for the trains to park in (at least, on the wooden coaster type. The train is stopped for what feels like 15-20 seconds before the restraints open. Killing my throughput game)