I don't think you can go wrong with any of those really - though I would definitely only use Indie as a nickname for India and would probably only want Charlie as a nn for Charles, Freddie for Frederick and Lottie for Charlotte. Yet I'd leave Alfie and Harry as standalones so there's not much logic there!
Based on your ideas, how about:
Archie, Ben, Bobbie, Bertie, Daniel, Eddie, Ferdi, Isaac, Jamie, Jonty, Joshua, Lucas, Monty, Noah, Oliver, Oscar, Reuben, Rafi, Sammy, Thomas, Vinnie, Wilkie, Zach
Anna, Chloe, Clara, Daisy, Emily, Flora, Georgie, Gracie, Hollie, Isabelle, Katie, Lily, Layla, Lyra, Lara, Livia, Lydia, Megan, Molly, Millie, Maisie, Poppy, Pippa, Ruby, Rosie, Sophie, Sophia, Scarlett, Summer, Tilly, Violet, Zoe, Zara