You are forgetting the implications of casting every int32 to int64. First, how are you going to feed a 64 bit number if the runtime value is limited to 32 bits? Second, you completely ruin memory optimizations and unnecessarily double your memory footprint. You mentioned iOS and Android but I think you forgot to consider that these devices don’t have 8 gigs of RAM. Hell, you’ll be lucky if you have more than 1GB.
There aren’t really any benefits of adding uint32/64, double, and int64. Chances are if you know how and when to use those data types you likely need to be using C++ anyway (yes I realize the generalization of this statement).