Just a random though but if they want speed they could consider making a typescript JIT instead of typescript -> javascript. Typed languages can run much faster than untyped. Maybe that's impossible with current typescript given anything can be changed, eg (30 minutes into running something does Math.floor = ... etc, but maybe some kind of escape analysis could help or maybe push for some new keyword to mark code as safe to optimize.
Building a new JIT for a dynamic language, if it is supposed to be competitive with JS compilers, is a project several orders of magnitude bigger than building a runtime like this.
TypeScript's design is very much that of a typing layer over a dynamic language. It's unsoundness and various loopholes to escape typing mean it's not much of a help for typed compilation.
