Another option, as many have said, is to plant the seed at the end of TLJ. One thought I had is that so much is made of the Resistance sending out a signal for help, and no one answering. It’s reinforced again in TROS. What if they did get an answer, from Palpatine? The radio crackles, and maybe we just hear his iconic laugh. Just a tease at the end to build up anticipation for TROS.
I know I’m late to this convo but that sounds incredible.
The one thing I wished we saw more of was a connection between TLJ and TROS. Bridging those two films together would have helped things immensely.
I wish there was some way to go as far as Rey’s parental reveal happening in TLJ, but I don’t know how it would work.