You can do this already today. Just need to add a few npm scripts to your package.json.
Take a look on how I did it for my Carousel plugin: https://github.com/manijak/nativescript-carousel/blob/master/src/package.json

"tsc": "tsc -skipLibCheck --outDir dist",
"tsc.dist": "npm run dist.clean && tsc -skipLibCheck --outDir dist && npm run dist.copy",
"dist.copy": "cp -R platforms dist && cp ../README.md dist && cp carousel.d.ts dist && cp package.json dist",
"dist.clean": "rimraf dist",
"plugin.tscwatch": "npm run tsc -- -w",

The only thing I've noticed is that watch & HMR only apply the first change, not the later ones. Even tho it detects them and reports that they have been synced.

This one major drawback of the seed. And this is why I use grunt to build my plugins TS to JS, having gazzilions copy scripts in the package.json is not that appealing...

I think I made this work w/o those copy scripts:

• Set the tsconfig.json to output the compiled JS in dist folder
• Change package.json file to point the main entry to dist/<your-plugin-name
• Add a script to run tsc in watch mode for the src folder.

This way when you make a change the watch will replace the files in the dist folder. And since the main points to that file it triggers HMR to update the app.