MIMF

Do any of you have thoughts on omitting the first fret inlay with a MOP block set? I'm building a 5 string bass and think it will look better if I start the inlay at the 3rd fret.

If you don't like it, leave it off! While it wouldn't be fun, you could always add it later if you or whoever ends up with the bass really wanted it.

I don't own a single guitar with a first fret inlay. I really don't think anyone will even notice.

In sets I've purchased that have the first fret inlay, I use it for something else like a headstock logo. It's your choice, use it or lose it unless it's supposed to be "historically accurate" (which seems like an oxymoron since no 2 guitars were the same back then).

This is really a matter of preference & personal taste. Some of the "big block" inlays can look a bit weird to my eye starting at the third ... like there's something missing... although it was quite common in the '30s. (Google old L5 & D'Angelico pics)
Depends on the inlay & guitar design. Maybe mock up (ie dry fit) everything with the inlays laid onto the neck, & take a shot with & without the first in place... see which looks better.

My opinion is like Dave's. I like the first fret inlay. It always seemed weird to me that they would start at the third fret.
It looks like something is missing. In the necks I've done, I inlay the first fret.

I guess I'm in the minority. I don't care for 1st fret inlays for a couple of reasons. First, I think the whole point of the inlay is to give you a quick reference-point to identify fret-locations in a hurry. I don't seem to have any trouble finding the 1st fret! Second, inlays are usually proportional to the size of real estate available and the 1st fret seems to command a giant one that to me, seems over-sized and cluttering the fret-board. I don't mind it so much when it's just a small dot.