If you play the career - like the one park, with the durability problem of rides (every few mins a ride breaks down and you should do a lot of refurbishments) - It would make this park nearly impossible.
Why should a refurbishment, like chaning the block brakes, or whatever affect the desirability?
I'm not sure, why it should be like this.
If you change the design, the coaster doesn't change. If ii's blue or green doesn't matter - changing the scenery could increase it a little bit, but I think the coaster is the same, so it shouldn't change that much.
Refurbishment is something like the abrasion or changing block brakes, so this isn't affected by such changes. (please correct me, if I'm thinking wrong about the refurbishment)
It's old, because it's in the park for a long time - like in real parks - a new coaster is more popular, than an older one - it's not because the older one is rusty.
I think it's perfect like it is. - if you want to change the sequences, feel free to change them - if you don't want to change them, just take the default ones.
Please don't get me wrong - I just do have a dissenting opinion about these points.