These aren't romhacks, but these are saves which have Alucard at level 99 with level 1 stats. There are two memory cards, one for US and one for JP versions. Each will have three saves:
1. Highest possible level 1 stats.
2. Lowest possible Level 1 stats
3. Luck Mode stats with 0 Luck
Gameshark codes work with 1.0 of the JP version of the game, and 1.0 memory card saves are compatible with 1.1 and 1.2 versions of the game as well.
You can learn more about these saves here:http://archive.foolz.us/vr/thread/1649195/
Since SotN romhacking is going nowhere, this seems to the closest to any kind of "challenge" or difficulty romhacks for SotN.
Of note, is that there are some differences between the NA and JP versions of the games. Many are already documented, but I seem to have noticed that it's much easier than the NA version. Around the Inverted Castle there is a big difficulty spike where enemies do huge amounts of damage. In my play through enemies did not seem to be doing much damage at all. I doubt that my armor was THAT good. There doesn't seem to be any documentation on the enemy stat changes from the NA and JP versions.