Export TIFF with with original print resolution

That 'resolution' value you speak of is simply metadata and has no bearing; you only need to worry about the number of pixels you end up with. Sure, you can have 1000x2000 pixels at 72ppi, 720ppi or 1000ppi and in all cases, you still have 1000x2000 pixels and you could alter the values each time. But the important aspect is the number of pixels. Add the metadata, or ignore it, you still have 1000x2000 pixels for print. 

Can you export them all and add a specific PPI? Sure but rather pointless. I agree 100% with the first answer here:

So in my opinion, you are spending time on something that doesn't make the slightest bit of difference.

The question is indeed why you think you need to retain the original resilution setting, which is just a number in the metadata of the image. As long as you do not resize on export, the exported image will have the same pixel dimensions as the original, regardless of what number you use for pixel per inch.

Digital images really don't have resolution in terms of ppi, despite what you said above and despite what you you see in the LrC export dialog. Digital images only have pixels, not pixels per inch. A photo with a ppi of 240 is the same as a photo with a ppi of 10. Not a pixel changes.

The pixels per inch only matters if you intend to print the photo, and even there, if you tell the printer you want a 6x4 inch print, you get a 6x4 inch print.

So in my opinion, you are spending time on something that doesn't make the slightest bit of difference.