Interesting situation. An enviable one at that as well. A few comments.
1) Sell your house? I actually like that idea. I like it because you expect another 25-30K decline in the next year. If this is correct it makes sense to take money off the table. If it is a home you love then don't sell it. If you want to upgrade your home in any way bigger, nicer, newer, better location etc. Then it makes sense to sell. Make sure you understand all the transaction costs moving, closing costs, commissions etc. You not only have these when selling your house, but buying your new one.
Getting access to credit. - This is a key point. Most lenders have some type of time restriction on when your house is on the market until you are able to refinance your house. Countrywide is 30 days and there are among the most forgiving. This means that if you try to sell your home and you fail to do so it must be off the market for 30 days before you can attempt a cash out refi. Most banks are much longer.
The heloc idea. Probably the best. Let me add a couple of caveats. Banks are still locking and closing these at this time. What that means is that let's assume you get a line of $200K 80% LTV. You buy one house with 40K down. Your thinking great you can go buy 4 others. There are rules about acquiring more than 4 properties with mortgages that are acquired by Fannie/Freddie.
I've also heard stories about HELOC's. The worst is the associate who had a 300K HELOC. The bank called it due, swiped 200K out of his account (it was the same bank). Talk about a bad deal on both sides.
PM me if you would like more details.