The reason I'm asking for an alternate solution than SimPE is because the version of SimPE that I currently use doesn't support renaming the first names of Sims, as it can completely render the neighbourhood the Sim lives in, making it unloadable. So I wondered if there was anything else that could expand the name limit of Sim's first names. Since SimPE does support renaming the last names of Sims, I won't need to request for any alternate methods of doing that, but I can't rely on SimPE to safely change a Sim's first name.

A massive pain in the side since it's faster and easier than doing it in-game, and there's a limit to the number of letters a Sim's name can have, unlike SimPE which is unaffected by that limit. Also there are certain names such as "Malcolm " that can't be typed up in-game, since it automatically removes the space at the end of the name. Malcolm and his grandfather and father all have spaces at the end of their names, making their names read as "Malcolm Landgraab II", "Malcolm Landgraab III", and "Malcolm Landgraab IV".

For Renaming Sims either First Names or Last Names get what I use, twojeff's The Sim Blender from simbology.com.
With The Sim Blender you can change any Sim's Name in the Neighborhood using the Phone menu and they don't have to be on the lot. It takes a few steps to change the Sim's Last Name, but it is easily done. Easy to have Malcolm Landgraab IV name his son Malcolm Landgraab V, and when the next generation is born easy to have the others named appropriately. Using The Sim Blender is the best method that I know of.

How are you trying to change the sim's name in SimPe? It doesn't seem plausible that doing that may damage the neighbourhood.
To change a sim's name you need to locate and open the sim's character file and change the catalogue description (CTSS) for your language, you may then want to update the name in the Object Data to suit (the game will do that for you next time that sim loads).

Thanks. I'll see if it helps. Though I probably won't check just yet.

I'm lazy so I just renamed Malcolm so his first name is "Malcolm IV" and his last name is "Landgraab." That way I only have to rename one sim and the surname stays the same from one generation to the next.

I prefer not to add those to the first names of Sims to be honest. I prefer to use SimPE to edit them in, and edit them out if newborn Sims inherit the number in roman numerals when they shouldn't.