Good Luck. You can do it.
It doesn't sounds as a good idea.
Maybe you can use microblaze and. Connect your hardware (written in
VHDL) to microblaze using OPB bus or FSL Link (Fast Simples Link)
available in microblaze.
If you decide for using OPB (it's shared and slow compared to FSL),
you can thinking about using IPIF (intelectual property interface) core
for facilitating the vhdl development of your core. If you decide for
using FSL (it's rapid and dedicated link), i suggest you reading the
xapp529:
http://direct.xilinx.com/bvdocs/appnotes/xapp529.pdf#search=%22fsl%20application%20note%20xilinx%22
Jardel Silveira
LESC - UFC (Computer Engineering Systems Lab - Federal University of
Ceara)