Aftermarket sun-roofs are not a good idea, since they involve issues of structural strength (roll-over cases & other accidents). If it is an original mfr's factory option, then one may assume that they have done their sums right & provided additional structural reinforcement. Since it is not the case here, but TML is providing it, one can keep one's fingers crossed & hope that TML has exercised due diligence!
BTW its been 2-3 months since Hexa is launched but still not a single car seen on road yet. I stay in Mumbai & travel for my office on a busy route but still yet to see newly purchased Hexa on the Road. Waiting to see one at least in upcoming days!