I believe speed of light won’t create a problem because we already are colliding protons in LHC at 99.9999% speed of light. The fact is in doing so we need to have larger size of collider or accelerator and LHC is about 27Km in Circumference with four detectors placed on its circumference far away from each other. So, to observe particle with even high energy is now depending on the way of observation and size of accelerator/collider.