Went for simplicity. As usual, I use multiple apps: dcraw, gmic, enfuse and darktable. Power of friendship. 
1 dcraw → linear 16-bit TIF of darkest and brightest exposures.
2 gmic → interpolate unwanted pixels.
3 enfuse → weigh for contrast.
4 gmic → smooth (guided) → brighten.
5 darktable → semi-auto perspective correction → crop.
6 gmic → global contrast → slightly desaturate → local contrast → sharpen (tone) → resize → sharpen (edge).
Edit: The image above needs more contrast. Changes in italics. Here is v2:
