Pretty sure those pierce/punch defensives cost barely anything as far as blocks per mass required too, 5% or less block to mass iirc, considering they can straight up turn 25% of system damage into armor damage, then reduce overall armor dmg taken by a further 25% that's pretty damn worth, that said, so far I've only used them on modular plating outside of my own build world, but i know ships like that take quite a ridiculous amount of shooting to actually harm in comparison to some cheap unarmored alpha dmg destroyer type, especially against the ever present alpha damage "meta" (Example of not giving 2 shits about strong missiles while on pure armor HP hurrdurr, [dat repair cost tho])
Further layers of pretty meaningful defense could include good AMS (or PD if you want) systems (multiple outputs, 360x360 rotation, secondary long range weapon for better detection inbuilt, these perform VASTLY superior to low # output/limited range of movement/RF Cannon only set ups imo) & lock on/swarmer distractions (I use a bunch of simple cheap "ships", basically factioned cores, that share the same name as the ship & are undockable via an inner ship remote, only takes 3 blocks per docked distractor & the onboard logic/rails to dock them, in return for a huge annoyance to your opponent trying to lock onto you, and his indecisive swarmers/missile turrets.
Modular plating really comes into its own when you're dropped to low shields as given a small amount of their own shielding they seem to "catch" shots that would otherwise impact & cut your own ships shields, with decent coverage you can become incredibly tanky during the period which your shields are low (low enough for rail objects to take damage) and your armor plates are still in good condition. Another type of non-docked 'Modular armor' that I've seen used pretty well is any type of forcefield/door/anything seperated from your ship by like 10-20 blocks on the front, severely limits the damage that those first few salvos of alpha damage can do so long as it's positioned to actually catch the missiles.
If you wanna actually get your missiles reliably through all of this shit, use AMS Distractors (Logic fired or manual, dumbfire or heat seekers, whatevs) in combination with Vertical/Horizontal/Even Reverse fire lock on missiles. Having missiles "Drill" into a target, IE hitting in a tight cluster one behind the other is preferable to wide checkerboard spreads or a single large missile strike, as they will more easily bypass the armor and focus on the squishy insides that they can really tear up. Cannons & Beams while lack luster on pure block dmg compared to missiles, just ignore the armor/block penetration problems inherent in missiles and are perfect for the real wetwork of destroying a good ship, IE destroying all the rail, turret, computer & weapon groupings that make said ship strong in the first place, correct me if I'm wrong but this is what is meant by "Delta Damage", while it's generally a filler dmg role in Eve online, it's got a much more vital role in SM due to the hybrid 'Actual structure' + technical HP system involved here.
