Couldn't you defeat ASICs pretty definitively (at least for a long time) by making the algorithm dependent upon a gigantic completely random substitution table?

Couldn't you defeat ASICs pretty definitively (at least for a long time) by making the algorithm dependent upon a gigantic completely random substitution table? It would at the very least require ASICs to have giant amounts of ROM or RAM (with a memory controller etc) which would multiply ASIC cost. AFIAK for today's ASICs a table larger than a few megabytes would be a strong deterrent. Go really big (e.g. 64mb) and you'd have some margin. This would also be completely deadly to GPUs, especially if combined with branches and complex algorithms. Edit: even worse: perturb the table using entropy from the block chain, making it impossible to burn into ROM and requiring tons of on-board RAM or a memory controller.