With regards to spacing I think that if you go for a bigger sail, like a 8.5, then you could switch the 7.5 for a slightly smaller sail. A 7.0 would work well as the biggest sail on the Kombat, and be a lot easier to handle than a 7.5.
A quiver of 5.3 - 6.0 - 7.0 - 8.5 makes sense to me. It makes sense to increase the spacing when you go to bigger sizes.
Looking at Severne sails a Gator 7.0 combined with an 8.5 Element, or a 7.5 Glide (that rigs on a 460 mast) would make sense.
With Gaastra a Remedy 6.9 and a 8.5 m2 bigger sail (or the 7.5 m2 Plasma on a 460 mast) would be feasible.
Two Sailworks Retro 7.0 and 8.5 would server you well, or with Simmer X-Type/V-Type in 6.9 m2 and a 2-XC in 8.5. Or one Simmer X-Type 6.9 and one Sailworks Retro 8.5 as they rig on the same mast bend curve (and Severne rigs on the same SDM masts as well).
I think it is a mast question more than anything else. What masts do you have? Do you want to continue to use your old masts? Do you want to omit a 490 mast?