A valid concern was raised about the use of maxscript.
To help provide fast exporting tools from 3dsmax sooner, I wanted to suggest that the entire implementation does not have to migrate from maxscript to C to achieve the desired performance.
Instead, just implement some C routines for outputting the larger blocks of data (such as vertex data). Then call these functions from maxscript. Exporting many other objects such as camera nodes and lights is not time critical. The maxscript implementation will be sufficient.
Eventually, a full binary exporter might be the right choice. But until then, a hybrid might help discreet deliver a fast solution to 3dsmax users.
just my 2c