Is it possible to use MRC with DS-CDMA-MIMO
OK, let me explain that for you. First, if you want to understand anything in engineering, it's recommended to write it in mathematical form, then try to solve it theoretically and build its code accordingly. Second, regarding your question, is it possible to use MRC for MIMO - CDMA,   Yes, that's possible, why not? 

Now, The code you provided is not right. Why ? all simply, first   check when using simple MIMO without spreading spectrum. You will see that first element in x, which is 0.7+.7i, is multiplied by the first column of channel H and so on. In case if you are using spreading spectrum, it means that instead of having one sample 0.7 + 0.7i, you will have N samples, where N is the code length. it means you will have N samples in the same duration of symbol before spreading.  So, all samples should be multiplied by the first column of H. 

I think it's clear now, right?  so you should just now check how to write the above answer in matlab. . .  for example check this command : 

r = [];
for kk = 1 : size(h,1)
                      r_1 = kron(x_s(:,kk),h(:,kk)); 
                      r = [rec r_1];   
                  end 

r = sum(r,2);  


Good luck.