I suggested only having it on cars with a digital speedo because if you're going to go to the level of customisation where you remove the tachometer purely to re-orient it, you'd probably fit a digital speedo too. Thus, if this was the only option we got, it might look somewhat strange alongside other non-modified dashboard instruments. If, however, the whole lot was customisable, then that probably should be available for all cars.
That said, it's a fairly minor thing anyway, as we already have a perfectly accurate shift point light in all cars even if you can't tell from the engine note.
Sam