Unless the manufacturer makes a kit to convert the unit to have a brush blade, any attempt to convert it yourself will be either dangerous or won't work well. I attempted to do the same to my Cub Cadet and the shaft/hub is not designed to handle any type of metal blade without extensive fabrication. The brush cutter attachments for weed whacked work very well otherwise DR trimmers accept a "Beaver Blade" which is like a chainsaw blade for the trimmer.
Many thanks! Watched a utube video in the DR Beaver Blade kit. Pretty neat, but your advice on trying to modify a Cub Cadet convinces me not to try it.
It would be nice to have a mini brush cutter to control my privet hedge, but it appears that it is not to be with the Ariens.