Interestingly, there was a specific printing technology for expanding the palette of colour printing, Hexachrome:

https://en.wikipedia.org/wiki/Hexachrome

Tried several times to use it in projects, but the customer always balked at the additional plate charges, even when they _loved_ the added vibrancy and colour range.

The only printer I know of who was actually successful using it to make money was in London --- took on spot colour jobs from other printers when the spot colour was inside the expanded Hexachrome gamut, allowing for a faster turn-around (jobs on the same stock were ganged up) and no charge for washing down a press to change out the ink.