There are lots of potential difficulties making a hybrid and I hope this thread generates a constructive conversation that helps you design your build.

I'll start with something interesting about the twice born star set. In almost all circumstances it is less effective than wearing another set with another mundus stone (e.g. hundings rage set and a max stat mundus is better than tbs with weapon damage and max stat mundus's... mundi... munduseses.)

However, on a hybrid there are two mundus stones that have double the usual effects of other gear sets. The lover gives both spell and physical penetration (unlike spriggans or spinners which only give one kind of penetration). The thief gives both weapon and spell critical (unlike mothers sorrow... you get the idea).

So if you are going for a hybrid in TBS you will get the most from those 2 mundus stones.

Edit - Just had another thought and I am a little bit excited about this build idea - if you go for an argonian and create infused jewellery enchanted to reduce potion cool-down, and wore the clever alchemist set then you could have a very high uptime on the +653 weapon and spell damage. Combined with the TBS you would have a build which has incredible sustain (through the argonian potion passive), and reasonable amounts of damage, crit and penetration - and you could do all this in heavy armor! Your stat pools would be quite low, and I have no idea what skills or builds would benefit from having these all round good stats, but it is something I will keep thinking about.