The guaranteed next step is to offer the volunteers a long term paid contract at the end of their term. This would probably be well above what they would be paid elsewhere (young men with no university degree, desperate enough to volunteer in the first place).
Run the scheme for a few years, and you will have a large number of, young, high-school-level educated people that are financially dependent on the army. Thus, a militarized society.
What could possibly go wrong?
Finland, Sweden, Norway, Switzerland, Austria, Brazil, Chile, Mexico and Thailand each have active conscription [1]. The slippery slop you describe is far from inevitable.
Also, if you have decades of mandatory conscription then there is no slope to slip. Germany on the other hand is now on a slope, since they regress from a fully professional army back to conscription. How much down they will slip, remains to be seen.
Active != mandatory.
> Mandatory conscription (which I have personally served) is for a fixed term, so your livelihood is not tied to the army paying your salary
You're seriously arguing that countries with mandatory conscription are less militarised than those with active (but not mandatory) conscription?