In addition, any spells you
wish to include as part of the ward construct
add their complexity values directly onto the
ward. It must all be cast as one spell.
IF you wish to include them in the same Ward construct, yes. But why would you? You
don't want your Ward to fire off the Landmine(s) if someone hits it because hey, some poor mortal might do it by accident and wouldn't that be a stupid way to get Lawbreaker? No, you create a second, single-shift Ward construct for an alarm, in case the big one is breached (not just hit). And you attach the landmine to the second one, not the first. As I said before, no limit to the amount of separate Wards you can add to a place. (it's just that a single big ward has the advantage of being harder to dispel or damage and you only pay for duration once)
The Paranetters' multi-ward would be done in a similar way. It is just a bazillion small (3-4 shifts) individual Wards. A sufficiently high roll from a powerful enemy will go through all of them as they got the same block strength but trying to destroy the Wards themselves? You got to hit them individually and that would take a lot of effort. And if you destroyed only some of them, repairs to those would be pretty easy. Good way of keeping out mulltiple low-power enemies instead of one big enemy. The wards in Edinburg would follow a similar philosophy, except they'd be multiple big wards instead of small ones.
BTW, given enough time a Wizard could make wards of ridiculously high strength if they knew how. Harry for example could put a mild consequence into a ritual in every single scene. Assume a scene is half an hour or so. 8 hours of work for a week makes for 200+ shifts of power, easily. Add another 100 shifts of power for the timeskip at a rate of +1 complexity per scene, plus another 50 or so for total declarations and you could
potentially have a Ward with enough power sunk into it to drill a hole through the Earth's crust.