i see your argument there, although i think it might come out a little... messy. remember, ice, if any form of block type sits beneath it, turns into water. also the time it takes to melt varies. i stick to an overhead water drop.
VERY complicated redstone lock i made a while ago but i forgot about XD lol,
You have eight furnaces... activate the right three and you will get through... heres the catch. You have to activate them in the right order. If you don't, lava will fill the entry way. If you do it in the right order then the water and lava will meet making a solid floor of cobblestone to pass through.
Here is a link to the pictures if you don't believe me http://imgur.com/a/XPdBW#0
amazing.... I MUSHT SHEE FOR MASHELF.
anyways, for all of you who are asking for the DL link of that map i mentioned, you'll have to wait. remember how i said i was working on the vaults part two?
well, it's there XD