Me too. Especially if it really is as simple as converting to classes. However, I (and many others) have been bringing this up over on the repo for several years now and there’s simply no interest in prioritizing this.
i do it manually, i have been getting it down to 80kb and less that way.
I do the same, but got bored around 150kb. Thanks for sharing, gonna steal your file and see if I can reach your level 
That seems pretty high. I use rollup as well and consider anything over ~2s too long for dev. Not a scientific number, but below that, I feel like the compile is instant. Currently, my compile time is around 1.1s.
Can you split the rollup config into dev and production? Then remove whatever you can from dev - for example, babel and terser.