It's pretty personal but if I were in the rebuilding mood it might be:

A smaller front chain ring. Rational being that most gearing in the mid to high range works well for me and I only use the granny gear for hills anyway so why not go as low as I reasonably can without effecting the other gear ranges. It would just give me a lower bottom end which is what I want. Changing the rear cog for a lower gear creates a larger range to jump up and down in.

Given that I might need a different rear derailer to cope with the chain length shift from high high to low low.

I have RF index shifters on my trekking bars, which I like but if I had my druthers I would do indexed on the rear and friction on the front. Rationale being that I like to micro adjust the front derailer and sometimes get chain drop or delayed shifting from going down from mid to low range.

I don't know what groupset is best but the discussion about good but not too good makes sense to me. For loaded touring you just aren't shifting in such a way that high end components will benefit as they might for racing (as an example). For me that also applies to going from 7-11 cogs. I just don't shift that much so that small increments make that much of a difference.

But that's just me. It mainly comes down to how much you want to spend upgrading. The best thing is to have a decent frame. Then probably decent wheels, then probably gears or cockpit (or both).

Here's trekking bars with twist shifters