Maintaining respect for the law around bail is far more important than the fate of this one guy.
As true as this is, most people who have skipped bail in the UK are UK citizens.
In the case of Assange, enter a guilty plea in absentia, judge deems his time in the Embassy to be equivalent to house arrest, and he is immediately deported to Australia with no prospect of re-entry to the UK. Deportation could be considered adequate punishment and would certainly be the fiscally responsible thing to do for the UK taxpayer.
It doesn't undermine the 99% of other bail cases where deportation is not an option.