I believe you have the gist of the tools required.
Scratchbuilders will try and use whatever trick they can think of to speed construction, especially when it comes to making details, because its the details that will kill you. But I digress...
For major construction, especially the polygonal shapes of a plate armoured subject, you just need to transfer the measurements to sheet plastic, mark the shape with pencil or marker, then get out a ruler and your favorite knife. (I use an OLFA snap blade knife for cutting 15 thou sheet and up. Trust me, you'll like it.) Don't try and cut all the way through, instead make a deep scribe and snap the sheet along the score. Albeit, this trick doesn't work well on 60 thou and thicker sheet, but you would only use such thicknesses if you needed to replicate the scale thickness of the subject's armour. And even before I went that route, I'd either laminate 40 thou sheet or just fake out the thickness of the plates ala the location of the weld beads, etc.
For curved shapes, I will use a french curve to guide the knife or a scriber, unless its a circle arc, where I will use a pair of dividers to scribe the arc/s.
For detail construction, for instance the frames around grilles on the engine deck, look to Evergreen (and Plastruct) for help there. There are a number of extruded shapes to help you here, angle "iron", T channels, I beams, H channels, as well as various rods and tubes. But its this phase of construction where your creativity works overtime. For example gun breeches tend to be complex assemblies of various moving parts with hinges and sliders and other goodies, and the whole point is to get the model done, not to build a working miniature of the main weapon. This is where you think of short cuts to get the appearance right, but not require milling out an actual breech block. But this is just an example, maybe its a driver's hatch, or a periscope that will require extra effort.
Hope this helps, but the truth is, every intricate construction detail will require some special imagination or creativity to get the part to look right w/o taking a gazillion hours of modeling to complete. Though sometimes, you just have to dissect the plans and build the silly thing from the bottom up or from the inside to the outside.
Meanwhile, to answer your question about tools...
I have a couple, but they're not inexpensive. I have a Chopper II from Micromark, and besides making nice square, 45, 30, or 60 degree cuts, I can set a stop block, and churn out a number of identical parts all the same length. Its the chop saw of scratchbuilding.
I also have a "Carl" pro-model rotary cutter (from Staples). Its supposed to cut paper & photos, but it works just fine on sheet stock. I cut through 10, 15, and 20 thou sheet, and it makes nice square scores on 30 & 40 thou sheet. This tool is the radial arm saw of model making.
On the other hand, these tools just speed things up, before I bought them, I made due with drafting triangles and a good knife. Good luck.