With all the furore the Skyrim modding forum has been seeing over the community's latest http://www.gamesas.com/topic/1485263-shesons-memory-fix-ctdils-thread-2/, I thought it might be worth a punt to put together something similar for poor old Oblivion.
https://dl.dropboxusercontent.com/u/2584752/Version.dll - Copy it to your root game folder (like you do with OBSE) and start the game/editor as you would normally (with the OBSE launcher or otherwise). An INI file named 'Moreheap.ini' will be generated in the same folder and should have settings to configure the initial memory allocation size (in MB) for the game and the editor. The default value for both is 256. Sizes can be no larger than 1024 and no smaller than 256.
I've done no testing whatsoever other than checking if it crashes that process outright. No idea about side effects and stuff either (or even if a larger heap affects performance positively). Feel free to play around with it.