Fist off, by trimming the 4 turnout exit lengths( to the siding under the controls), you could gain ¼"-½" and shift everything else away from the wall a tad more. this would make the 2-S turns less pronunced too. (straighter; you are removing excess angle. (+base trimming is needed on at least one in a pair)
Changing them to a larger dia or NUMBERED (scale style). turnout is another way to bring parllel tracks closer when opposed to form an S and straighten the angles during the change too. (some large dia turnouts are pre-trimmed for this and include an extra piece of curve you simple leave off for closer spacing of parallels.)
You only need to climb about 5"; so you are ahead of the normal grade game already (eyeballed off the KW...? Get the exact rise measured between tops)
You might be able to pull it off by narrowing and shortening the lower loop to 27"x?" and starting the grade in the left corner closest to us, going up to the wall, then to the right and up again to the apex. Id add a tall plexi fence along the lower left side from wall fwd and right along the bench face about 5" as downhill derailment will definitely head right for the floor in those curves.
Add a reverse loops to compliment looping the grade both ways. (cool anyhow to never have to touch a loco or train to reverse it) You will be limited in length of trains, but I suggest experiments anyhow to see if dealing with a grade while actually running is "for you" as well as for learning your equipment's limits better. Id clear the lower bench and set up the L shape to try it (up needs the most attention).. Scraps of paneling and lumber are near perfect to stack for a temporary set of piers. (paint um grey for cement?)
A step grade is fun but also takes constant throttle attention without auto block voltage control on the grade or command controls. (not to hard really)
The other options: tunnel under then main bench and cut a long hole to rise out of on the main bench, or adding 3" along both bench faces and adding the grade right there. Another bridge or tunnel to keep your lower body and cloths from interfering while doing this 3" reach over.