I would love to see new trains on it, and the cave needs some updating. There are a couple different companies out there than make new trains for Arrows, I've never ridden them but I'm sure there is somebody out there that could do it and do it well. If Verbolten is a success they should get the guys that did the event building to work on Nessie's Cave.
I think the trains are fine. Nothing wrong with them right now.
I really don't like how the ride speeds up, then slows down over and over again. Get rid of one of the mid-course brakes (are they even necessary anymore?). I'm sure they're put there to increase capacity/allow two trains into the interlocking loops, but since the ride isn't as popular as it was in the 70s and doesn't run two trains into the loops, there's no need to have two.
If someone can enlighten me on that it would be cool.
I'd love to see tunnel effects come back too, but I heard that the fog was messing with the electrical stuff inside. Maybe keep the strobes/sound FX without the mist.
As far as the tunnel goes, use fog instead of mist, it would give a more eerie feel. They should have a realistic monster in the cave that moves it heads toward you as you fly out the cave, or at least a cool, realistic statue monster. Strobes would be cool, but what about black light instead? Revamp the effects, replace a few and make it look cool. Also, make the inside of the cave, a cave. Plus with black lights, people who aren't compatible with strobe lights would be able to ride still.
In regards to trains, I think it is fine. New trains could be a possibility within the next few years, I'm sure of that. After all, look at how old these trains are, and how many spare parts they have left?
The only problem with a statue or head coming out at you is that 1) it's pretty tight in there and 2) you move pretty quickly, so the timing would have to be perfect.
I think it could work but it would be tightly spaced.
Or another idea could be to put the monster on the outside of the cave looking down at you roaring and you escape at the last second into the cave, sort of like JP at IOA.