I definitely thought of this as well, and I like the idea of teleportation pads. They can be late game, maybe require space science packs, and plenty of them, as well as enormous amounts of resources to build, but I definitely DO want something in the game that allows me to quickly get from one end of the factory to the other end.
The fact is, huge parts of your factory simply don't need to be revisited once it's done. If you want to you can still walk through it to have a look, but usually I don't even do that and rather zoom in and move around using the map to have looks at the factory quickly. Actually getting around on foot, even with robolegs and pavement everywhere simply takes time, and it's not an interesting use of your time at that point. Especially if you're a tad forgetful, end up on one side of your base, remember you needed something else, or simply need to be on the other side for more maintenance or whatever the reason is, and you have to do another 4 minute hike through the factory to do a simple thing somewhere. It gets old. It gets really, really old.
Walking through a late game factory to me gets just as old as manually hammering away at ore patches.
Trains help, but walking to them and waiting for them is still NOT an interesting use of your time. In a game that is all about automation to improve your overall quality of life, personal transportation is sadly forgotten beyond the use of cars (which are often hard to drive through factories) and trains, which still often require a lot of walking and waiting. Mods may help, but I don't want to have to rely on them. Besides, it would be much nicer to have something like this supported officially with the 'proper' graphics, or style of the game, than something fan-made that might look off in the base.
In terms of teleportation pad mechanics, you can still do interesting things with it, like using a teleporter pad might use tremendous amounts of energy and might only be viable with enormous amounts of left-over power, which means you would need enormous amounts of steam engines, capacitors or a proper nuclear power facility with plenty of horse power to spare, or risk draining so much power that for the duration of the teleport your laser turrets might not function.
You can have a build-up period for the actual teleport to happen that draws such huge quantities you might actually depower your entire factory for the duration.
On top of that, as I said earlier, you can make it extremely late-game tech, requiring space science, which means essentially you've already 'won' the game, and there is nothing new left to build, only more expansions and whatnot.
Only thing I do know is, something needs to get into the game to allow much faster travel in the late game.