Leave TC as it is and do everything with plugs ins.
My opion: Plugins are 'bad'. They often dont integrate seemless.
Core only:
Plugin functions are move to the core.
Ultimate integration
TC gets bigger
Core but selecteble:
Looks a bit like plugins

But more integrated
Certfied plugins:
Lets face it.
Some plugins are buggy/slow/ take up lots of resources.
When some plugin crahes ppl will say TC crashed again.
And not TC is great/small/fast but the plugin crashed.
So maybe the most stable plugins get a certification.
Bundled plugins:
The best of the best gets bundled with TC.
Readily (installed)
If the author of the plugin aproves that of cource....