Once Aikar implements this, he could make the spawning exactly as vanilla, except it would be on netherbrick everywhere. The idea of spawning just in fortresses will be broken, hence why he's doing this in the first place.
I have a few questions: 1) Has nether chunk spawning changed since 1.2? In other words, do nether fortresses spawn in different places in 1.7 than they did in 1.2? What about the versions in between (since chunks outside of the original 5,000 block circle have been generated since 1.2)? 2) Can block-by-block (or at least chunk by chunk) wither skeleton spawning be turned on and off with an external program (like mcedit)? 3) Would it be possible to create a filter or program that can detect which blocks (using 1.2 chunk generation) would normally spawn wither skeletons and blazes? If not, could you at least detect which chunks naturally contain nether fortresses? 4) If (2) and/or (3) are true, could you use another filter/program to add wither skeleton spawning back in at the proper locations? Basically I'm suggesting you create a program/filter to run through each server's nether map and place wither skeleton and blaze spawning back in. I don't know how hard that would be to code, and I don't know how long it would take a computer processor, but it would give a really good end result.
It would only be possible to detect where they normally spawn using the seed, and that is what has caused the problems over the last few updates.
Here is the answer to all questions, kind of at the same time. Yes, structures have changed significantly since our maps were first created (Mainly with this last update). Bukkit actually created the solution you are probing around for, which required updating to the 1.6.4 thing Aikar mentioned in the OP To avoid this lag which can not be turned off, Aikar is turning to this alternative solution of creating fake fortresses more or less. Your block-by block change thing. Mojang changed how structures are saved... So no, that wouldn't work.
We will never be able to revert to 100% vanilla code. Mojang designed this (like everything else) for single player and 4 man servers... ===== For those who can understand technical things, the problem is mojang stores the entire worlds structure data in a single file. Mojang obviously understands large worlds can not be stored in 1 file so they broke it up into chunks.... But this was totally overlooked for structures! So essentially, for a server as large as ours with soooo many chunks generated, our structure files would be gigabytes! every time the server loads... entire file has to be loaded, then sit there eating up memory... Then, every time it saves, that file has to be written back out. This is what caused those massive lag spikes every 15 minutes when we updated to 1.6.4, it was the server saving... and that was before we even let the file grow too big.g Because guess what else is saved in these files? Mineshafts.... aka, all over the entire world and massive amounts of data I don't even understand why since nothing special spawns in mineshafts :/ I'll try to get it close to vanilla, but main goal is usable and what works best for players.
All nether brick items wither should be able to spawn And I feel they should spawn randomely throughout the Nether like Witches do in 1.7 in the Normal World, this gives people a chance if fortresses are too laggy, Or too dangerous or they just can't find one
i mean it really isnt that hard to find netherbrick in the nether..... i think the random spawns are a bad idea wither skellies hurt and the nether is already dangerous enough
I'd like it if they had the ability to spawn anywhere in the Nether however only on Netherbrick. That would mean that if you wanted to fight one you'd know it was coming, they couldn't just spawn anywhere As for light levels I think any light level would be fine ass the Nether doesn't really have light levels as such
I agree with most of the people here - nether brick and light levels. Also, I think a height restriction could help - something like between y=48 and y=70 (not sure about the exact numbers, but most fortresses are in that range). If you were to limit the default structure loading to only nether fortresses (not mineshafts), would it give a big enough reduction in lag? I wish I knew more about the structure.dat file format - it seems like wither skeletons spawn in a really small area, and that saving only those areas wouldn't take up much space/performance.