Would uterine perforation at the time of hysterectomy push you to recommend pelvic RT in a patient who would otherwise receive cuff brachytherapy?

It very likely would. I suppose that various factors could impact the decision, including the usual prognostic factors, patient's general condition and co-morbidities, etc. But, yes, a uterine perforation at the time of hysterectomy would represent another risk factor that would push me to be more aggressive, i.e. external RT instead of cuff brachy only. Having said that, for patients with reasonably thorough node dissections that are negative, I would consider treating a smaller pelvic field, e.g. true pelvis rather than whole pelvis, which would limit the risk of acute and/or late morbidity.