Alternate Upgrade to keep my unlimited data (on VZW)...Will this work?

[Lyfer]

I have three lines, two eligible as of right now, and a 3rd dumb phone. I know that the only way to retain the unlimited data is by buying the phone outright retail. But I've heard that if you did an alternate upgrade you could work around it (and ultimately retain the unlimited feature). So here's what I'm thinking:

Current Setup:
Line 1 - Droid X - Unlimited data - Upgrade eligible
Line 2- IPhone 4S - Unlimited data - Upgrade eligible
Line 3- LG flip phone - plain jane $9.99 line access (upgrade comes up in june 2013)

Use Line 1's upgrade as an Alternate for Line 3, then activate it on Line 1 (and reactivate the flip phone back on line 3). Wait a 1-2 days, use Line 2's upgrade on line 3 again (and revert flip phone back on). I've been told that the warranty would drop so I would have to pickup applecare or squaretrade.

My goal ultimately is this:
Line 1 - Samsung Galaxy S3 or Droid Razr HD Maxx - keep unlimited data
Line 2- Iphone 5 - keep unlimited data
Line 3- LG flip phone - plain jane $9.99 line access
(and throw my Iphone 4S fs/ft to make up for the price of upgrading)

Would this work? Thoughts?

P.S. Sprint and Tmobile's coverage is awfull where I live and I get a 22% discount with VZW.