I agree that there should be a cap for the maximum time a warp in could take, I didn't explain my self fully since I was just throwing out an idea I've had for quite som time.

When a Warp Gate is selected large spheres indicating quicker Warp ins appears.

Let's say hypothetically the max warp in time gradient is achieved at 20 range from closest nexus, with there being a minimum warp in time and a maximum that is constant ouside the Nexus sphere.

Or like many of you commented:

A gradual warp in time could be unintuitive, a similar effect could be achieved by having two constant warp in times, one within the nexus sphere of influence and one outside of it.

Now that I see these two options I'm certain that having two constant values is clearly more inuitive and serves most of my intended functions.

However for the sake of argumenting for gradient warp in calculated from the Nexus:

The way Protoss expands with gradient warp in times is very interesting, as the Protoss could take agressive forward expansions if going for Warp Gate centric tech. There is an interesting dynamic to be had that is lost with two constants.

As a result of having the gradient warp in times the dynamic range could be made much larger before warp in time cap is reached, perhaps up to 30-40 range!

The gradient warp in time might be too complex and unintuitive though as mentioned before due to the difficulty of judging how long a warp in will take. The solution to this could be as simple as showing the number next to the cursor when warp gates are selected.

I'm terribly sorry for any mistakes with formatting as I am on my mobile at the moment of writing this.