Brazilian R4 NTSC DVD? Really interesting, and a good find!

Happy you are considering MultiAVCHD; it sit in my HDD for literally years, before I decided to use it extensively - read: make my own custom menu - and now I use it for every project.

Well, it is not the first BD regrading, and sadly I think will be not the last... personally, I like most the original one, with no so crushed blacks as the BD, and without teal skies... maybe I'll increase a bit saturation and decrease brightness, but just a little bit.

You have two choices, if you want to retain the DVD/HDTV grading (as I think you would):

use only the HDTV as source, and apply the grain plate over it, with a lower overall quality, but perfect color grading
regrade the BD using the HDTV as color reference, with a better quality but probably a not perfect color grading match.

Your choice, but I'll try the second; if the difference in color grading will be too much, then I'll try the first; to be sure, just make some fast tests using the most offending (color wise) shots - let's say, three shots of thirty seconds each, to save time; they will be the ones to base your initial choice (that could be changed later if needed, of course).