Hi Willie,
In this case yes, but in close cooperation with efneo.
Not right now – first we need to convince David from Taiwan to make more beltwheels for us.
(We need a special BCD for the efneo - common 80 t beltwheels are not suitable.)
Made to retrofit into all single (or dual) speed bottom brackets.
(Maybe in future also to replace the KS3 for EVO.)
Sorry, no clue about the costs (so far, even the shown drive wasn’t paid to its seller 
)
Once there is a complete kit available it won’t be a question of „who can“ – the question is much more „who has all the tools“.
Principially you can refer to the Schlumpf installation thread, the efneo kit installation would be pretty equal (Except the torque lever positioning and the shifting cable routing for the efneo).
Re: Has anyone retrofitted a schlumpf on their strida?
Absolutely yes – please do refer to the gear ratio thread linked above – you can expect in high gear 14% increase.