@gregorysonofcarl, thanks for the suggestion and the help!
In a first step, I plan to only have the brushes that correspond to the current Pencil2D tools (Pencils/Sketching, Pens/Line-art, Brushes/Painting, Erasers and Smudge). This way, the user experience is not much different from the current application while having a much better brush engine as currently. If the brushes you are talking about fit in the Sketching, Line-Art or painting category, we may add them straight away.
We may include more tools in the future but it won’t happen before having a first stable version of Pencil2D and before being discussed of course!