You should read the correspondence of the founding fathers.
Well, there's a lot of it
They spell out very explicitly that the right to bear arms applies to individuals,
Is the "individual" explicitly distinguished from a mobilisable citizen / reservist?
The "militia" includes all able bodied men between the ages of 18 and 40, not just members of an established militia.
Which basically is what the Swiss army is, right ? Civilians with a military training than can be gathered / mobilized quickly when in need. If feel that he "established" distinction is only meaningful in the context of a modern state / army (as an example London police was established in 1829, replacing a "disorganized system of parish constables and watchmen").
and that the purpose of that right is to curb an oppressive government.
My understanding is that the opposition is between states militias and federal standing army, not between civilians and either form of government. From Wikipedia, the amendment was basically written to please the anti-federalists.