I also prefer 2 (Lem arrives at the top of the tunnel they create). Everything else is just a rebranded version of the L2 Laser Blaster, merely using a different tool to avoid confusion with the NeoLemmix diagonal Laserer.
At that point, a "flexible Laserer" that works more like a destructive version of the L2 Roper or Archer (i.e., with the player being able to decide the angle with a second mouseclick) would make more sense to me.

Obviously, that would require both changes to the established Laserer AND be a lot of programming effort (there is a reason we've ruled out the Roper and Archer early, and went with the more straightforward Spearer instead).
And since I always warn about making more changes to established skills (as much as I do enjoy the Freezer now), I only brought this up as a thought experiment.

I actually still think the diagonal Laserer is versatile enough, even more useful than a vertical Laserer, oftentimes - because
a) the shafts are Walker- and Shimmier-friendly, not just Climber-friendly, and
b) they're also Faller-friendly, not just Floater/Glider/Slider friendly

.
For the same reason that we don't need a vertical Laserer, though, I also think we don't need a Driller that stands still on the ground.The unique features of an upward Digger are not merely restricted to the angle of the shaft, but
also to the position of the lemming. The Twister / Driller / Propeller could move upwards through terrain, which neither the Climber nor the Laserer nor the Ballooner (or a Glider in an updraft) can.
Many advanced levels rely on having to manipulate the positions and directions of movement of individual worker lemmings (oftentimes several workers at once, rather than a single "pioneer").
The Laserer is pretty useless in such levels - aside from its ability to shoot a Shimmier from a ceiling, if timed correctly.

In NeoLemmix, that's your only option; in SuperLemmix, you can also do this with a Spearer or Grenader.
The Twister / Driller / Propeller, meanwhile, could easily swap positions with another lemming, by moving upwards through terrain and, in doing so, creating a shaft for other lemmings to fall down.