That’s a solid start. For bullet‑proofing, start with a base layer of reinforced steel or composite panels behind the paintings—so a single hit won’t get you inside. Add a second, spaced layer of concrete or gypsum; the gap will absorb shrapnel. Keep the paint low‑gloss, because high‑sheen can reflect sensors. Install motion‑sensors on all entry points and a silent alarm that trips to a remote feed. Build a false floor that slides out into a trench for quick escape. Finally, use a low‑profile, non‑magnetic locking system—no easy access for lock‑pickers. Stick to these layers and you’ll have a place that’s hard to breach and easy to monitor.