Not the author but I'm making a similar tool currently, and the reality is no because of the nature of it being character based.

You can theoretically have "artistic" polygons where it renders using a mixture of characters to emulate how that grid would be filled if a certain shaped was laid over it but the end result wouldn't be very functional for the purposes of diagramming.

https://cascii.app can :)

It's not an ascii renderer, but a ascii diagram drawing tool