You went over X% on the heat bar, ammo exploded. Over 100%, you melted. It was a placeholder, basically.
With a few bits (ghost heat, notably,and changes to prevent easy-booms of ammo) tacked on, MWO cruised along to the modern day. The placeholder system, missing the critical parts needed to actually make heat matter in anything less than total Dire Wolf Death Star situations.
This has led, in part to the massive laser/PPC banks of utter destruction (and it's cousins the AC/20 duo-o-doom, etc. etc.). Why? The actual prices for overheating a 'Mech never got put into the game, only the "good enough" mechanic we have today. Other kludges like ghost heat (which punished boating only because it shoved people towards 100%+ overheat faster) were glued on over it in an even uglier, inelegant attempt at balance.
This isn't insanely difficult to fix- clearly the game tracks overheat % as it stands, and all that needs be done is adding appropriate effects. We can translate decently from the 0-30 heat scale in tabletop- 1 overheat in TT is basically 3.33% (repeating) in MWO heatbar.
17% overheat = 'Mech temporarily acts as if it's got an engine rating of (normal engine - 'Mech tonnage), meaning it loses the appropriate speed and agility. Jump jets are NOT changed by overheat, giving you a reason to use them for an escape after heating yourself into slowpoke mode.
27% overheat = 'Mech gains a very modest cone-of-fire effect (crosshair visibly expands slightly). LRM spread increases slightly.
33% overheat = As 17%, only (normal engine - 2x 'Mech tonnage).
43% overheat = COF expands, LRM spread increases.
50% overheat = As 17% only (normal engine -3x 'Mech tonnage).
57% overheat = COF expands again, LRM spread increases again.
63% overheat = ammo damage of .1 per tic, randomly applied to a single ammo section per tic.
67% overheat = as 17%, only (normal engine -4x 'Mech tonnage).
77% overheat = ammo damage of .2 per tic instead of .1, randomly applied to a single ammo section per tic.
80% overheat = COF expands even further, LRM spread increase.
83% overheat = As 17% only (normal engine -5x 'Mech tonnage).
93% overheat = ammo damage of .3 per tic instead of .1, randomly applied as before.
100% overheat = autoshutdown unless override
100%+ overheat = 'Mech damage as per normal MWO rules.
I'd suggest movement reduction caps at the "one legged 'Mech being hit" speeds and agility at the equivalent of the 'Mech's tonnage in engine rating (to see it in action, slap a 100 rated engine in a 100-ton 'Mech).
With this, heatloading your 'Mech carries offensive and defensive penalties- even a "I'm only needing to fire once" boater will have to deal with sluggish movement and people riding the heat curve while firing will lose accuracy as they raise their heat level until they let the 'Mech cool down.
Lighter 'Mechs may peak in heat faster but still retain mobility, while heavier 'Mechs will keep a sharper eye on the bar (but be generally able to sink more heat) to avoid going full-on into slug mode.
In other words, you'll actually have to pay attention and there's a price for those immense, 'Mech-coring beamstrikes.
Once a real heat system is in? Kick ghost heat to the curb and re-examine the pile of "fixes" we've awkwardly had placed in MWO.
Edited by wanderer, 10 September 2015 - 12:50 PM.