The 7th wasn't rebuild as such by this point but restructured. They were introduced to front line duties in stages as and when German ground forces needed extra punch. For Crete there were four regiments, the Assault Regiment (gliders) plus FJR1, FJR2, and FJR3. Post Crete only the 4th battalion of the Assault Regiment was left intact and FJR2 effectively ceased to exist for a while. The surviving troops from the Assault Regiment and FJR2 were used to reinforce the other units. The airborne troops available amounted to no more than 4,500. That's not to say they couldn't be used in an airborne operation, just that it would be a weakened force.
After the war a German study on airborne operations was conducted and a report produced by Helminth Reinhardt. Contributors to the study included the likes of Kesselring, Student, Meindl and von den Heydte.
The following extracts are from that report:
Since everything Germany possessed in the way of parachute troops had been committed in the attack on Crete and had been reduced in that campaign to about one-third of their original strength, too few qualified troops remained to carry out large scale airborne operations at the beginning of the Russian campaign...
The lessons based upon German operations may then be summarised as follows: In airborne operations cheap successes cannot be achieved with weak force by mean of surprise and bluff. On the contrary, airborne operations which are to achieve success on a large scale require a great outlay of materiel, outstanding personnel, and time for training and preparation. Such operations are accordingly "expensive". From 1941on Germany, in comparison to its enemies, was "poor".