I haven’t seen anyone use anything other than the laser Snipers to set front geometry. I’ve seen the ads for toe plates and other lower cost methods but I have literally never seen them used at the track. The point of this is the price point for the lasers seems acceptable for most and those that don’t own their own set, borrow from others.
I personally like the Snipers and would never consider using anything else because I don’t have to turn on my brain due to their ease of use. I’m not saying stringing is rocket science but it does require more expertise to use and I can’t imagine it being nearly as fast as the Snipers.
I do like your thought on stringing on the ground but getting everything level would be a bear and making sure you take out the variables associated with wheels, tires, etc.