No one has done it, but I was interested in doing this too.
I am not an expert in transmissions or ECU stuff by any means, but I would have to guess that since we have a model hear of this car that uses the VQ35HR which is very similar to the VQ35DE, and it has a 7at transmission that the odds of getting it working would be good.
You would want to start by finding out if the bell housings are the same or not (they probably are). If the bell housings are not the same, then the trans wont just bolt right now and you would have to do some work adapting it to mount properly. If the bell housings are the same, next you probably want to look into the wiring harnesses for each transmission. Are they the same? Or what differences are there?
If you get all that info and it looks compatible, the next step would probably be to talk to a very good shop that can do all the advanced tuning and is capable of doing top quality engine work and all that, and give them all the information about the project and see if they are willing to take it on. Depending on how the ECU interfaces with the TCU, you may be able to skate by keeping your stock ECU with probably a flash, but you may have to shell out for a nice aftermarket one that has more options for wiring and access to more parameters. Theoretically, the ECU difference between the motors should be ok, since the difference between DE and HR is almost nothing. I think just oil pump and intake stuff. But Im not exactly sure how the interaction between ECU and TCU works, and whether it simply wont "handshake" if the ECU is expecting a 5AT model TCU and vise versa.
The cost of a swap like this could range greatly. It all depends how cheap you can find a quality 7AT transmission for, as well as whether you have ECU-TCU compatibility or not. My guess would be probably around $2250 on the low end if everything is compatible and you can just bolt on and do some flashing, or as much as probably around $10000 if you have to adapt the mounting, buy a new Haltech ECU, do everything from scratch. At that price, it would be easier and cheaper to sell your car and buy a newer model with a higher gear trans.
edit: oh and when looking at whether the bell housings are the same you should also look at other specs like the length of the trans. The 7at may end up being longer. If the lengths are not the same then you need to have a new driveshaft too. You could probably get away with an oem driveshaft meant for the newer 7at trans since your rear diff mounting flange is the same, or if you are going to have the 7at trans built out for higher power (like from Level10
), then also just have a custom driveshaft made by The Driveshaft Shop
since they can make you one in carbon fiber for around $1k that will greatly lower your drivetrain mass on the car and support the higher horsepower.