I think Bun helps with the memory pressure, granted this is relative to V8. I'd pushback on the certainty with the reality that TS provides a significant drop in entropy while benefiting from what is a sweet spot between massive corpus size and low barrier for typical problem/use-case complexity. You'll never have the fastest product with JS, but you will always have good speed to market and be able to move quickly.
I wonder how much of a lost in the middle effect there is and if there could be or are tools that specifically differentiate optimizing post compaction "seeding". One problem I've run into with open spec is after a compaction, or kicking off a new session, it is easy to start out already ~50k tokens in and I assume somewhat more vulnerable to lost in the middle type effects before any actual coding may have taken place.