"Full speed" randori with joint locks...? Forgive my lack of experience but aren't they mutually exclusive. Are you saying that you would attempt ikkyo, nikkyo, sankyo, (or any specific technique for that matter)on the first of four guys coming at you at full speed? I've never tried but it seems that as soon as I successfully lock up one attacker I'd be dead 'cause the other three are no longer coming at me full speed, they're there taking me down full force.
I've always been taught that randori is practice in principles not techniques. Mainly irimi and tenkan (blending). Whether you irimi/tenkan with nothing or with an atemi is where the choice lies.