AIUI, Brad is looking for a cost effective system for setting out simple steel frames. I think we agree that a robotic total station is not appropriate for that type of work. So what might be better than a line laser but not as expensive as a total station? The theodolite to which I linked is similar money to the laser and would do a better job at establishing perpendicular lines.
It is possible to set out with a theodolite on your own. Lay a tape measure or levelling staff down where the sightline will be and read off the value that the cross hairs intersect. Then walk down the field and put a mark at that number.
With an inexperienced assistant, you can do the same: instead of 'left 20mm, right 12 mm, ad infinitum, you just say 'put a mark at 124mm on the tape'. Once they do that, they hold the pencil upright on the mark and you check it is correct.
A theodolite is also useful for plumbing steel frames and with some forethought (clamping a horizontal ruler near the top of the column with the 100mm mark aligned with the flange) can also be done on your own and without leaving the ground. Modern theodolites do not invert the image.
Tbh the best option is to pay a setting out engineer. Especially if you have a lot of jobs and can build a good working relationship with them.
Then there are one of the many setting out lasers on the market if you want to do it yourself.
Yes you can do it with a theodolite but we have moved on from there. Same as we can do it with 3 tape measures.
I got the impression that the aim of the post is to update working practices, not just move sideways.