To get an ult for any legend, it is enough to upgrade the legends to G12 or R1 and give the minimum modules. But for the ultimate for Kylo and Rey, you need to upgrade them to R7 and give them the best speed top modules. Although these legends have long lost their value and are not able to withstand new legends or characters with omicrons.
When does these events ease? @CG_SBCrumb, @CG_Tusken_Meathead