if you want to have 8 buttons in each cell of las column that makes 64 independent buttons. I think grids internal editor support will not help you in this case because they were designed to show the editor only on selected cell, the exception is cbsCheckboxColumn which shows a checkbox always, but that is custom drawn
if the grid is not scrollable, I guess you can do it pretty much by just caculating the coords of the 64 buttons and put them on the grid, if grid it's scrollable you have to take in count some events in order to reposition them.
other way doing is like the case of checkboxcolumn, drawing the buttons your self, using themes support you can draw the buttons to look much like ordinary buttons, in this case you have to handle mouse events on buttons your self too, but you only have to draw the 1 button eight times at different position using OnDrawCell, in this method scrollable or not doesn't matter.