A possible way to limit suicide heavy bombers is to limit trim authority to the airspeeds and trim levels the planes had during their normal service use. If the plane can't be trimmed to dive at high speeds, it'll be very difficult to get a stable dive bomb platform in the heavy bombers. I'd think that before a diving heavy bomber could get lined up on the target, either the wings would rip off or the plane's natural pitch trim condition would cause the nose to start rising regardless of how much nose-down pitch force was applied. If the speed increases too fast, the wings rip off.
Also, bombs simply won't separate from the aircraft below a certain G level or with a relative G vector that doesn't point straight down the mechanical release pathway and out of the bomb bay. Many (most?) heavy bombers had simple gravity release mechanisms that required positive Gs, and a G load vector nearly straight out of the bomb bay to get the bombs out of the bomb bay. Release them at under 1 G or at an angle, and there is an increased chance that the bombs will hang up in the bay or cause bomb to bomb or bomb to aircraft contact and possible detonation while near the aircraft. Simulating release limitations in G, airspeed, sideslip angle, etc. would almost entirely kill suicide dive bombing in heavy bombers. A heavy bomber relying on gravity release for safe bomb separation would be unable to release it's bomb load in a stable dive beyond around 60 deg dive angle. The bombs might come off the rack, but they'd just as likely end up in the cockpit after bouncing around inside the bomb bay and against each other.
Requiring a relative G vector that is within 20-30 deg of straight out of the bomb bay for safe bomb separation would be quite realistic. For more realism, have the bombs detonate immediately after they arm if they are still within 20 ft of the aircraft, simulating bomb to aircraft impact. I've seen video of this happening in RL when a bomb was released outside of release parameters.
I'm not sure if it's not already done, but do the wingman bombers actually try to follow the lead bomber down in the dive, or do they disconnect when past a certain dive angle?