The available space in the handle of WalkEasy crutches is a cylinder of about 26mm by 120mm.
That frontage will need to accommodate (at minimum) the LED optics, switch, and charging connector.
Users dexterity and adaptability
The controls must be rugged enough for daily use but still be usable for those with limited finger control.
People will use this in the rain, so it will need to have a basic level of water resistance.
High-powered LEDs can create a lot of heat, even more so with the proscribed 100 lumen brightness requirement I have set. Combining the need for a heat sink with the need for water resistance will be an interesting challenge.