Hi Emily
Again I would be looking at which programs are causing the high server load and limiting them to specific times of day. If not, maybe you need to look at general system performance and tuning of system to improve server workload?
As mentioned, I don't believe there is anything SAP standard for this but it seems like you are trying to use security to fix a system performance issue. I've been in cases where accounts are locked for specific activities (like payroll) but that's been done manually via SU10 and then unlocked after activity.
Regards
Colleen