The worst thing for European security is for europe to become a military rival to Russia (, the US, China). This is a likely to be an increasinly popular desire for the publics of europe now that the US is withdrawing, but it's a dangerous trap -- the upside is that you retain a seat at the table, the downside is you will be grinding down your population in wars and military spending.
The german model was the european model: spend almost nothing on defense, let the US provide the nukes, sit back and get rich.
One reason this model may fail is the UK and France -- both are expeditionary forces (the UK where-ever the US is, and france in africa) trying to play at being a great power. This only ever worked because the US was prepared to bail them out whenever anything bad happened (cf. Libya). Without the US, both nations may try to drive towards EU military unification and hence genuine great power status.
Good luck balancing the Chinese, Russia and US defense budgets. Europe's spending will be crippled, just as the US's is -- without global currency status to prop it up.