I was planning something similar...
We miss playing heroquest, but as the GM I cannot really be botherd with learnig yet another complicated rules system. So...
...I just use the shadowrun rules with magic. No Matrix, bodytech or guns. In the basic rulebook and Run and gun there are pletty of rules for mellee weapons, shields and armour. The one rule change I did implement, was that while mundane chracters cannot create enchanted items, but may use them. So you can get a magic sword that can hurt magical threats....
Then we go dungeon crawling.
I suggest you try that with your player group, and see how it goes. There are plenty of RPG Fantasy setting books. Just pick one that you like
Try that with your players group and see how it works out.