I was encouraged to create an account and post this here. If there is enough interest, I can write and submit a formal guide. Credit to Paulygon on GameFAQ's, as I got the codes to do this from the list posted on there.

Following these instruction will result in a CH5 in which all characters start at level 1 and starting equipment (and Alena will have the Thief's Key); basically a guaranteed equal start for the purposes of speedrunning and racing CH5 only.

You will need Game Genie capability. These instructions conform to the limitations of the original hardware; max 3 codes at a time and no ability to toggle them on/off during play.

Chapter 1:

To begin, use these two codes to trigger the chapter end condition: EEOAPTAP UEOAZVTY

Start a new game the usual way

When the king finishes his speech, exit the castle. The other soldiers will not move; this is OK

Save at the House of Healing and power off/on to return to the GG code entry screen; saving the game saves the flag states, so the first two codes are no longer needed

Enter the following codes: ESSXYISA TEVZASYT These codes set the XP bonus Ragnar receives at the end of CH1 to zero.

Enter the castle and talk to the king to end the chapter

Save at the prompt and power off/on

Chapter 2: NOTE: Don't worry about the Thief's Key; it will be in Alena's inventory when she joins in CH5

Enter to following codes to trigger the chapter end condition: EGNEZZAG KANELZSA

Escape the castle as you normally would

Walk far enough to get Cristo and Brey to join (possibly not required)

Reenter the castle

Walk upstairs; the castle is now empty

Walk around and exit the castle to end the chapter

Save at the prompt and power off/on

Chapter 3:

Enter the following codes to repair the bridges: LAVKNNIE VEEKXNIY

You can cancel random enemy encounters with the following code to make this part easier: ATXOSIAZ

Leave Lakanaba and walk to Endor

Save and power off/on

Enter the following codes to complete the tunnel: LAVKNNIE AANKKYAO XXEKXNIN

Walk through the tunnel to end the chapter

Save at the prompt and power off/on

Chapter 4:

Start with these codes; they will move the NPC in Haville blocking the gangplank out of the way, allowing you to board the ship without a boarding pass: LAVKNNIE PANKKYAP EEEKXNIN

After the opening sequence, walk through the theater house (possibly not required); do not leave town

Save at the House of Healing and power off/on

Use the following code to freeze the day/night cycle (VERY IMPORTANT!): SXNGUSVV

You can cancel random enemy encounters with the following code to make this part easier: ATXOSIAZ

Walk to Haville

Board the ship and set sail to end the chapter

Save at the prompt and power off

You may now remove the GG and start playing CH5 as normal

Oddities:

Because several flags are not triggered, there will exist several minor quirks in the world state. Most of them will never be encountered during a speedrun, but some are worth mentioning:

Orin will be in his spot in the Cave West of Kievs (where you get the magic key). You can talk to him but he won't join your party.

The Inn and Weapon shop at Frenor are not available; everyone is still waiting for the Fake Princess who is not there.

The Fox village is active. If you enter it, you can escape by talking to the mayor, just like in CH3. There is no way to break the spell, as you can't get the dog.