Not sure if I understood your last post correctly, but if I did - you should not have an issue where you are forced to withdraw mostly penalty eligible earnings. This is what you should do 401k related (if you have the money)
1. max out your regular 401k and get the match whatever it is
2. put as much as possible as quickly as possible each year into your after tax 401k (up to 51k- regular 401k contributions-match to a max of in your case 20k)
3. As many times as you are allowed to each year (should be at least once) do an in-service withdrawal of all the after tax 401k money to your Roth IRA
Example - In 2013 you put 20K in your after tax 401k subaccount - by the time you do the inservice withdrawal in 2013 you will have 22K so you will move 22k to your roth ira and pay tax on 2k for 2013 tax year.
4. you will likely be able to withdraw the entire 22k out penalty free and tax free from your roth ira 5 years later (additional earnings on the 22k cannot be withdrawn until you are 59.5). If you withdraw the 22k earlier than 5 years you will owe 10% penalties on 2k.
Separately (and probably before you do this after tax 401k trick), if you don't have money in a standard IRA (if you do, you can still do this, there is just a bit of prep work first), you should take advantage of a backdoor roth ira (http://thefinancebuff.com/the-backdoor-roth-ira-a-complete-how-to.html
) - the entire 5500 you do from this should be withdrawable immediately (provided you don't have other money blocking it).
Basically you should be able to put up to 56,500 in a tax advantaged accounts each year with the entire amount put in Roth IRA each year withdrawable penalty free 5 years after you put it in.
Note, and this is important, that if you cannot do in service pre 59.5 non hardship withdrawals at least once each year from your after tax 401k subaccount - this is no longer a good strategy - this is because for the time the money sits in your after tax 401k subaccount, if it sits there until your retirement and is not moved to roth ira every year - you are trading ltcg tax rate for deferred taxes at ordinary income rate - generally not a good trade.