I was actually thinking the same thing, Razor Rocks in particular would make for a VERY interesting speedrun. I haven't run it yet, but videos exist of it being done in under 3 hours... And those aren't speedruns.

I think a 90 minute time is doable. That would be one custom coaster every nine minutes on average... But it would probably have to be faster since the coasters need to be financed somehow. Once the category opens, I'll submit a run once I get one under 90 minutes.