Well Yes you could block the hole if you wanted,but for safety sake I would fix it so it does work,but as a short term fix yes it could be blocked off.
The job of the decompression value,or should I say jobs.
1.To make it easier to start,as without it it could and would kick back,and believe me it hurts.
2.Helps to keep the engine from over-revving by releasing the compression at its highest end,therefore helping in slowing the engine down and keeping it within a safe rev range.
That's why when somebody asks me when they have problems with a decompression value and want to replace it with a spark plug I always say no and advice them of why.
After all Victa just didn't install them so they could make extra money,it was put there for a reason.As listed above.
I hope that makes sense.
