I take the question to mean, can you aggregate the Thunderbolt ports such that multiple cables with max throughput of x4 lane are combined to produce x8 or x12 lane throughput.
I know it can be done, since one (to remain unnamed until I have permission to name them) production company built a custom switch (at a huge price) that aggregates Thunderbolt in that manner. I believe the price of that switch was somewhere north of $100,000.