Ok am not familiar with the term 'non-reentrant.' but it sounds like you want to re- enter the task while it is in the wait condition.
You can not re- enter the task but you can re- start the task. In the Tasker edit screen click the cog icon upper right (properties ) set collision handling to 'Abort existing task' this will kill the current running iteration of the task and allow a new iteration to run.
To achieve the 're-enter' status you could break your long wait condition into a loop with shorter wait times and include a if condition to monitor outside conditions .
1. Wait 2 seconds
2. If %Stop_loop matches 'stop'
3. Do other stuff
4. End if
5. Variable add %loop=%loop+1
6. Goto 1 if %loop <10
Not the best sudo code but it should give you the idea.. :)