For breakfast benefit,

From my limited experience at Marriott's North American hotels (St Regis SF, US Grant San Diego, and W Hollywood,
Their breakfast is not those buffet type, but more of a la carte orders.

Asian hotels, such as St Regis Singapore, Tianjin, Bali, The Athenee Bangkok, Keraton Jakarta, Westin Jakarta, Singapore, and Mina Seyahi, all provide buffet breakfast.

I can guess the added cost to allow extra elites on those buffet will be much lower than those North American a la carte breakfast.

For other issues like lack of upgrades, I guess its depends on property themself