I didn't take any ABRSM diploma exam, but completed FTCL of Trinity by self-learning.
In my humble opinion, I think it's a bit ambitious to attack 5 works, though your Brahms capriccio is not a long one, unless you are very well prepared, esp. in the Q&A section "viva voce" (as you need to deal with 5 composers and know their lives and compositions).
Your proposed one is a balanced programme, but can be more balanced. Chopin, Liszt and Brahms belong to romantic period. As others suggested, you may consider to take one or two of them out and include a post-19th century work instead. I don't know all the composers and works on the syllabus. though I suspect that Ravel, Debussy, Messiaen, Webern are popular choices for this category. I would rather suggest that you may also explore John Ireland (e.g. his April is not too hard technically). There are certainly numerous off-syllabus choices, but I think it's rather up to you to fix the core, 'I-must-include' pieces first.
BTW, you actually don't need to play the works in the order of 'period', which many did: baroque -> classical -> romantic -> post-19 century. This gives some flexibility and room for you to think about. Say, if you must have Choipn Ballade No 1 and Liszt Un Sospiro, I am not sure if I want to hear them one after another immediately.
Good luck!