Maybe you'll find my post https://arathunku.com/b/2023/moonlander-keyboard-layers-tour... helpful with oneshot modifiers across layers but also keeping Shift and Ctrl accessible. I really hated any timers / held vs tapped on home rows, it prevented me from fast typing and rollovers. Now I really only have space bar on hold/tap that's used in usual writing but it's on my right thumb and have never been a problem.