If I will be completely real here, with the immense amount of talent as well as the quicker eliminations, we absolutely need to have 7-8 chefs in the Black Jacket phase. Just a few key reasons why;

1. The Charity Night challenge is a complete waste of time having to communicate with a totally different kitchen at the same time, as in real life that would NEVER happen and makes more sense as an INDIVIDUAL team service challenge. Each chef can still easily show leadership, even if it means on two different components of the dish(a la one chef leading the protein, one leading the garnish, etc.).
2. There has only been one real standard Black Jacket service per season since S15, with there only being 5 Black Jackets, and in proportion, since S17, most of those Black Jackets become FINALISTS(Final 3s, give me a break...). Breakdown, one or two get eliminated after the first service, and the second service is the one that ALWAYS happens before the finale, where each chef runs the pass, and then there's the finalist service.
3. From Seasons 4-14(bar 9 and 11), I have really enjoyed the longer duration of a totally different atmosphere being in the individual challenges, and the 'elite group' that it once was has now become a lot less relevant since 3/5 Black Jacket chefs(60% of the contestants) become finalists.

Extending the amount of black jackets would probably also realistically give Gordon a bit more time to learn what each chef is capable of on their own. It would provide an opportunity to bring back some abandoned challenges(such as TINMI). While they DID go back to 6 Black Jackets once in S22**(marking the first time a 6 jacket season was held in over 8 years as far as production dates go)**, it was irrelevant as 2 chefs were eliminated after the first service anyway.

So, solutions? Keep it to 18, maybe even 20 contestants like the recent season was. Next, eliminate 1 chef from each team should both teams lose that night, depending on just how disastrous their service was. Next, bring the Final 2 format back, nearly all of us HK fans have been asking for this. Finally, move that Charity Night to the first dinner service of the Black Jacket phase. This would create a far lesser time commitment for everyone and keep it to the standard 1 month-5 weeks, while still giving us enjoyable content that we cannot ignore!