There are already some extensive collaborations. For example, Dutch divisions now report to German command. And the French and German armies coordinate on a lot of things and we're all NATO members of course.
There are some calls for bringing back military service in some countries. I'm not sure that's needed or a good idea. The reason most European armies are not in great shape is not a lack of people but years of budget cuts and mismanagement. That would be because they don't actually do a whole lot of fighting normally. They defend without ever being attacked and there is the odd mission abroad where some countries send maybe thousands of troops at best. I don't see that change any time soon. And that's a good thing. I count myself lucky to not have been exposed to major wars close to where I live. And I live in the middle of Berlin. Buildings here still have scars from WW II. At least the few that survived that.
The most credible threat on our eastern border was the Russian army. And courtesy of their own ineptness, they seem to be hard at work reducing that threat by expending most of their officers and usable equipment in the Ukraine. It doesn't look like they are recovering soon.
Also, there is the point of this being a remarkably old school conflict. The Russians tactics have barely evolved since the 1940s. They seem unable to use their airforce effectively, their navy is not a factor either. Mostly they are just launching wave after wave of cannon fodder at their enemies. Brutal and it's not working great for them judging from the recent news.
Most modern conflicts are very different. Relatively poorly trained conscripts don't add a lot of value in such conflicts. Europe needs lots of rockets, drones, etc. Keep the fight far away from its borders.
A bigger risk would be an armed uprise within our borders. For that reason getting a lot of small countries excited about building out their armies is not a great idea. I'm old enough to remember the Bosnian war and I've visited Mostar a few years ago. Political populism and armies are not a great mix. A lot of blood got spilled in Europe that proves that.