Maybe the --bwlimit option of rsync? It will not pause, but slow down the transfers, so the target can be able to write the data.
For example, if you use --bwlimit 300 it will only transfer 300k a second.
If that doesn't work, you could use the -v option so you get output from the rsync command. Then pass the output of rsync to a script that reads 1000 lines, and pauses for some time before it reads more.
Here's a slow reader script:
while read line
if [ $count -eq 1000 ]