The ability to store experiments on probes is a small change that would impact hugely on game play. The objective here is, while on a far away manned mission, send all the experiments you gathered back to Kerbin, on a much smaller and lighter craft. An alternative to storing science on probes is to provide a small, light-weight science storage unit that can be attached to a probe. The unit would draw a constant amount of electricity, to preserve the experiments. This option would open the possibility to go a very long exploration mission carrying a bunch of small probes, which could be sent back periodically as you gathered science. Wouldn't it be fun to be on the ground of Eve and watch you little science-filled probe shoot up to the sky, relatively effortlessly, on it's merry way back to Kebin?