Since Uppaal language allows sophisticated type declarations and function calls with those types, I think it would be great to implement some optimizations to avoid creating and copying big blobs in temporary memory and hence gain some performance of already slow virtual machine (no benchmarks for this and I don't really know how Uppaal handles copying of temporary variables, but my experience with integer loops tells me that it is 100x slower than compiled C code).
Here are a few links to get started:
C++0x way of dealing:
Visual C++ approach of explaining things:
perhaps it is worth implementing "T&&".