Yes any good tuner should be able to tune it but it will take longer being a first time tune and getting to know the software which will ultimately cost more and finished tune may not be spot on and require further tuning, costing more again. When tuners have a lot of experience with a particular ecu they know the ins and outs, potential issues, bugs and how to correct them. Since you like the Maxxtuning ecu so much, why don't you take the plunge and put your money where your mouth is and show us all how good it is.
For me it makes no sense when we have so many locally supported companies to choose from and if I was gonna build a no expense spared monster setup I would be going Motec and it wouldn't be on a r33 gtst. The end.