In theory, yes, I think you should be able to buy a tank. However, it is so cost-prohibitive, it isn't a viable option for most regular citizens, and certainly not me. It may be more "fun" as you say it would be, but way too expensive for anyone on an average income. But, the second amendment is there to protect the people from government taking away their natural rights. Taking away gun rights and the people's right to defend themselves always leads to government overreach and less freedom. A well-armed citizenry is a backstop to prevent the feds from going too far.
There's a reason that all of these mass shootings occur in areas where no guns area allowed (I realize that armed citizens in the LV case probably wouldn't have mattered, but most of the others it could have). People that can't fight back make easy targets.
Most "common sense" gun control proposals are just politicians' attempts at using emotion and sympathy to bring more and more tyranny to this country and that their solutions will result in more victims and more death, allowing more opportunity for government to seize power.
Also, the 2A has nothing to do with sport or hunting. The Constitution was written at a time where the people needed the same firepower as the British government to defend themselves against a tyrannical government. People that claim to believe in the second amendment and the own a gun for hunting, but would support someone else's rights be taken away, really are lying- they follow a Animal Farm approach to gun rights- that their rights are more important than the other guy's.