Hydraulic drilling rig attachment on excavator

I want you to design , prepare cad drawings along with list of parts required to make an attachment which can be connected to a 20Ton excavator by removing the bucket and using excavators own power to drill holes in hard rock..the attachment should have a remote easily accesible to control drilling by the operator along with safety considerations..the attachments which are made by OEMs are very very expensive. I want you to design it so that i can make an attachment under 3lakhs rupees.