And thank for the great review and honest feedback.
The tubes of the handlebar are standard and you can easily remove the grips and add a set of your choice, extensions included. You can check the Pimp My Halfbike topic for some ideas >>> halfbikes.com/pimp-my-halfbike.
As to a sturdier and larger model for taller/heavier riders - yes, developing an XL version of the Halfbike might be a future project and it is on our to-do list. However, it is still just an idea and not something we will be able to offer in the nearest future.
Happy rides! :)