I would like to please request that the Level 50 option be added to Gens 1-3, like all other gens.
In Gen 1, this is relevant for the official formats of the time, such as Nintendo Cup 1997. These formats used a level range, meaning your Pokemon could range from level 50 to 55, but the total of your three Pokemon sent in battle had to be below 155. In practice, this means that the most common level for a Pokemon to have is level 50.
Nintendo Cup 1997 has seen an increase in activity recently, and it is a format that many players, myself included, play on a frequent basis. Having a level 50 option on the calculator would be greatly appreciated, as it would speed up many calculations, including in the heat of battle.
In Gen 2, it is the same deal. The official formats of the time, such as Nintendo Cup, also used the same level range, and the same conveniences apply there too. This is another format with a vibrant competitive scene, although it is still mostly focused in Japan for now.
In Gen 3, there are a number of formats that would benefit from a level 50 option. The official tournament format of 2005, Pokemon League 2005, was played at level 50. This format has been "revived" in the form of Orre Colosseum, which is played at level 100. However, many of the subformats of Orre are played at level 50, matching the in-game Colosseums that inspired their rulesets. These are formats that are played on a very frequent basis in the Orre community, with regular tournaments, so again a level 50 option would be very appreciated. It's also worth mentioning that the in-game facilities such as the Battle Frontier, are also played at level 50, so this option would also benefit someone using the calculator for those purposes.
Currently, all formats from Gens 4-9 have a level 50 option. I see no reason to omit this option from previous generations, when it would clearly benefit a number of formats which are both popular, and also happen to be "official" competitive formats of the time.