Heh, what do you know, I started doing a project on the very same area, ie. Lähde sector. I was kinda planning on having the 'Millions' 3d printed myself but in 1/72 - but I came to the conclusion it would cost a bit too much (and probably take ages) to print, even in pieces and without roofs and floors. So it's back to the drawing table.
Another issue I have is that nowhere I can find maps with trench lines drawn of the area, all you can find is the location of various bunkers / korsu, and the general line of tank obstacles & barb wire, maybe some tank traps thrown in. So my enthusiasm kinda ran out there. But I intend to pick it up again one of these days.
It's probably best just to scratch-build bunkers and trench using the traditional methods. Let me know if you need any information or sources, I got a couple of good ones, and being Finnish, I can get to the original sources maybe easier? I would be curious to see the maps you mentioned...