On all the Evos I've owned
R888 were fine in the wet it's just if there is standing water with such and extreme tread pattern it cannot get rid of the water underneath the tyre sufficiently enough so there is a risk of aquaplaning.
To put into context
Did a wet track day at bedford Evo 9 with R888 window wipers were needed 40 + cars going around but still not enough to dry track out until late afternoon.
I was still one of the fastest around the track the only thing that was remotely close was a cayman S not a fast car but handles great but they still couldn't keep up with the R888 they develop so much more grip than a standard road tyre that even in moderate rain the increased grip level is higher than the wet performance of a standard road tyre.
Opinion only the MPSS are a great road tyre and there is the problem stick some real heat into it and it will go off quickly and understeer and ruin your day as every area of the car will be effected braking,Corning,acceleration and what is a trackday for other than to lose the restraints of road driving
I personally will not buy another set of wheels just get tyres swapped over couple of days beforehand for yourself buy tyres if you like the R888 buy another set of wheels and flog them on when you sell car.