The reason I like modeling narrow gauge is that there have been so many little NG railways with oddball solutions to their budget restrctions than anything I'm going to come up with with my lack of skill is likely to have been done somewhere sometime on a prototype NG railway
So do go for something like On? using large bodies on HO/OO gauge bodies. As you will see on the board I once worked a 2ft railway with a scale of 8.25mm/foot on 16.5mm track and called it 8.25n16.5
You must have a computer to access this site so you should try drawing your stock, buildings on the computer and making your own kits. I only had a B&W printer in those days so used felt pens to add pastel colours after I had reinforce my paper prints with cardboard. Kellogs cornflakes provides quite large sizes for buildings etc. With my saw I made a saw bench and 'milled' say 3x3mm sticks to put in the corners of buildings for stability, as well as building a stock pen for a siding on the layout. Also a derrick with three legs and boom . Then a water tower using a tin from the kitchen with wooden supporting structure and so on .... The key to clean cutting here is to have some scrap ply which fits close around the blade. Back then I was using a 3/8th chuck Black and Decker saw with the B&D 'skill-saw' attachment ... earlier this little saw had done most of the woodwork in building the family home we lived in at the time.