Although this is ultimately up to your GM, the way I've been running Iron Gods is that the Semi-Automatic description is a bonus, not a restraint: you can make iterative attacks as normal, but if you don't get iterative attacks you can still take multiple attacks using a semi-automatic weapon as a full round action, and that stacks with Rapidshot if you have it.
The text for Automatic weapons also, iirc, specifically calls out that they *may* be used as Semi-Automatic weapons at the user's discretion, as a toggleable choice.
As evidence for that, I'd point to all of the NPCs who use semi-automatic weapons and get iterative attacks in line with the above -- Book 6 has one on page 47, for example. In Book 4, page 58, a character with a technological rifle and +10 Base Attack is listed as having, in their attack line, "zero rifle +15/+10 touch (2d6+4 cold)" -- that's clearly an iterative attack offset by five and not the flat -2/-2 that the text of Semi-Automatic calls for when making multiple attacks. My read has been that this character, with that statline, could elect as a full-round action to:
- Attack twice at +15/+10 (iterative)
- Attack three times at +13/+13/+8 (iterative + semi-automatic)
- Attack four times at +9/+9/+9/+4 (iterative + semi-automatic + rapidshot)
- Attack in a line (since the rifle can fire on automatic mode)
Those other options aren't specifically called out on the NPC pages, but that's in line with how feats that you can elect to use or not use are not always included in NPC statlines.
All of that's moot if you GM disagrees, obviously, but I would argue that the clear intent is for semi-automatic lasers, etc, to be used as often as your BAB allows.
