Here is an idea that doesnt involve consolidation of Guren+Senei, but still frees up 2 buttons

Remove guren and senei from the hotbar

Make Ikishoten grant the buff "enhanced Hissatsuken ready"

The enhanced hissatsuken effect upgrades Shinten into Senei (lv72 trait), and upgrades Kyuten into Guren (lv70 trait)

That way there is still the option of doing either AoE or ST, still have the two skill share CDs