> Hence realtime sprite scaling is not feasible.

Playdate got STM32F746 (ARM Cortex-M7F) at 180 MHz. 320 kB SRAM (and 16 MB of other RAM, maybe PSRAM?). DSP and saturation instructions are included.

The display is 400x240 1bpp.

Surely that's more than enough juice for sprite scaling? (Might need to copy graphics data to SRAM and even to do it in tiles for better performance.)

Although your video based implementation is pretty cool.