I've found that the biggest difference in woods is in the mids - what we tend to perceive as "brighter" is often just that they stand out more with a dip in the mids or low mids. Ash, to my ears, is pretty scoopy in the mids (Leo Fender, notorious hater of mids, used it for that reason), maple seems to generally have a higher mid bump with a lower mid scoop, which can "brighten" a guitar, but there are plenty of excellent sounding all maple guitars that aren't excessively bright. However, in most cases, these differences are pretty subtle - I have a few guitars with identical builds with ebony or maple fretboards, and the tonal difference is minimal, with the biggest difference being in note attack. And even that is subtle enough that I only notice over time. I couldn't pick them out in a blind test.
So, with a 7, you can go a bit lighter in the mids to get the clarity for the lower strings, IMHO. The Loomis has this combo, IIRC, so it works.
However, I feel that other factors affect wood more than the species - it's an organic material, so a lot of variation will "muddy the waters" a bit. How the fibers transfer the different frequencies also depends on density and mass. Sustain is another component, as well. Hard, dense pieces of wood will transfer energy more efficiently, and preserve the rapid oscillations that reproduce high frequencies, while lighter, more "open" woods will give you less sustain, but mellow the highs, possibly giving the guitar a more pleasing warmth. In the 70's, players were looking for as much sustain as possible, so they loaded guitars up with mass - heavy pieces of wood, brass "sustain blocks", even making guitars out of stone. However, nowadays, a lot of people look for the lightest guitars they can find, feeling that the lighter wood resonates more freely, giving it a more pleasing tone. So it's a balancing act.
Swamp Ash and Maple both have a great range of density. I had a Kubicki ash strat that was heavier than any Les Paul I've owned, and it sounded like ass. But I had a "Lite Ash" series tele and strat from Fender that sounded great.
All THAT being said, I really don't think you can "ruin" a guitar with your wood choices (by species). A good piece of wood is going to be a good piece of wood. Just take care to get even, resonant pieces that meet your desired balance of sustain vs tone, and build away!