How apparently attractive design choices can cripple a navy

How could a designer secretly weaken a new northern European navy in 1920 without being immediately exposed?

Build fast but lightly protected ships, restrict anti-aircraft elevation, and make submarine batteries hard to maintain or replace.

The traitorous designer would choose defects that could initially look reasonable. Speed would be emphasized while protection was stripped away, producing impressive trials performance but fragile combatants. Anti-aircraft mountings would have limited elevation, leaving them better suited to low torpedo bombers than later dive-bombing threats. Submarine batteries would be difficult to replace and repair, turning an ordinary maintenance burden into a persistent readiness failure.