Due to the length of the things I want to talk about regarding the randomizer. I couldn't fit them into a few tweets so I thought I go back to this place and pen down my findings and thoughts. I would not discuss the technical aspect of a randomizer or the features I would want as those are really subjective and really depends on your personal preference.
First things first, let me just show you guys what my settings are when I play the randomizer. I do not think I need to mention there are spoilers as you need to complete the game to access the randomizer.
Note that both "Defeat True Evil" and "Defeat All Evil" essentially need the same key items. Defeat Gebel is the only option that really doesn't soft-lock the game most of the time.
To complete the randomizer in my setting you need 2 things, "Dimension Shift" and "Zangetsuto".
Dimension Shift is needed to get into Dominique's boss room which is literally blocked by solid walls. Zangetsuto is needed to get into Den of Behemoths.
Let's talk about the common problem that everyone is running into, getting Zangetsuto.
In the randomizer, there are 4 places that you can get Zangetsuto.
1. After the 2nd Zangetsu fight from Zangetsu himself (Original location in the normal game)
2. At Dian Cecht Cathedral in the chest where there is a path that leads to Hall Of Termination
3. At Hall Of Termination in the chest of a secret room which on the way to Gebel's Boss room
4. The Gold chest after beating Valac boss of the tower of twin dragons.
If you do not find Zangetsuto in these 4 locations, your randomizer seed is soft-locked and you cannot proceed further as Zangetsuto is likely in the other 2 key chests which you need Zangetsuto to access.
That is probably the biggest frustration when you have a decent good run to find yourself unable to proceed further.
For this, I guess the should be the main focus of fixing in regards to the randomizer as this issue comes out so often.
Now with the second rarer problem. Traversing through the castle itself.
With how the game map is designed or simply how a 2D Metroidvania is designed, you restrict players from getting to places out of sequence in 2 main ways.
First, you can restrict the amount of height a player can achieve. Second is blocking places of entry with soft-walls like water, energy barriers, or literally a locked door.
For Bloodstain, the upper part of the castle is restricted from access mostly by height. The lower part of the castle is restricted mostly by water so you need a shard that allows you to "swim". Note that I quote swim. I get back to it later.
In my successful runs of the randomizer, I almost never need to go to Underground Sorcery Lab. My crazy fast runs also do not involve me doing the bottom part of the castle which you need shards to "swim".
So a crazy fast run would just need you to get "Dimension Shift" from Craftwork boss and getting Zangetsuto from the key item chest in Dian Cecht Cathedral. From there you are good to go to Den of the Behemoths and fight Dominique.
I do not want to too much into how to get around places with certain shards and it will just make this piece longer than needed.
With this case, you can easily see that if you get any shards that force you to go to the bottom of the castle. Your run is almost certainly going to double in the time needed to complete it. But there is something more problematic if you think about all the shards that you need to traverse the castle.
If you are unable to get any shards in your run that allows you to gain more height to reach the upper part of the castle. Your run is also soft-locked.
Which means if you get blood steal, deep sinker, aqua stream, craftwork shards. You are also locked out of the game.
But wait you say, there is still high jump shard that the randomizer assigns to any enemy. Yes but again if there isn't any that drops it you are still stuck.
For the second issue, I am not sure if there is a good way to get around this by the developers. They could introduce logic to have an enemy at the lower part of the map drop high jump always. I do not know if there are good solutions for it as I never developed games before.
So for now I decided to put aside Bloodstain randomizer as I am tired of going into a seed I cannot complete.
P.S. Regarding "swim". You can technically "swim" with dimension shift but the more interesting thing is swimming with "invert". I also found that you can use reflect ray, upgrade it to the longest possible distance, and force Miram into a position to get to the other side of the way. Looks funny but it actually works.
