In fact, I came up with the idea of Spaceship Delay a long time ago already, I just decided to give it a go for the KVR DC 16 when I saw that KVR organized again a contest this year. The thing is I have all the Korg Monotron little synths at home, and even if I don't use that much, I love the idea behind, and more specifically I love this one :
https://www.youtube.com/watch?v=CNXOI1AIjKo
So I was thinking : what if you could use it as an effect ? And what about designing a convenient plug-in to do so ? A few hours later, I was coding a simple Korg MS-20 filter simulation, and I put it into a delay line. And it sounded already really amazing ! Then, 3-4 weeks ago, I started coding a plug-in using that simulation as a basis, and the all the important things that we would want in a good delay plug-in. I had also the chance to rent another amazing device, called the Dynacord Echocord Super 76, which is a tape delay machine with a spring reverb, more focused than a Roland Space Echo, but which sounds really good too. Now I don't have it anymore, but I have studied it for a few weeks, and I had captured some impulse responses from it. So, I decided also to include a simulation of that spring reverb thanks to convolution also, and I am very happy with the results. And I gave a go to the modeling of a synthesizer Twin-T filter you might know as well.
Then, I did some digging about all the things that people like in delay plug-ins, and about the associated technology. I worked on a prototype which allows me to use different kinds of delay lines, using various strategies for fractional delay (linear+cubic interpolation, artefact-free implementations of time-varying allpass IIR filters), and delay changes (with or without pitch changes). I tried to put various audio effects in the delay line path, and kept only what sounded the best. I added also extra filters on post processing and a phaser, and the attack mode I loved from the Guitar Gadgets delay. I also saw that video which made me want add a freeze button and increase a little the maximum delay value.
https://www.youtube.com/watch?v=LhkXNCmctHw
I had also a very good idea for the user interface, which is why I called my plug-in "Spaceship Delay", but... unfortunately I underestimated a lot the amount of time necessary to make it a reality, so with a lot of frustration, I had to keep using the prototype user interface for the KVR DC 16 plug-in itself as well. However, I plan to update the UI when the contest is done ! And I got that idea of putting a manual / tutorial embedded in a plug-in for a long time, from the moment I saw that feature in Ableton Live. I was thinking about putting it in Guitar Gadgets 2 years ago but I didn't have enough time. For the KVR DC 16, I did succeed, and I'm happy with the result there too. Designing something like that for my recent JUCE Summit / ADC talks might have helped too.
I'm very happy to do that contest again and I hope I will "perform" better than last times but still, I know I will learn a lot of things again !
I think it's probably a easy to solve issue.
Moreover, I think the actual state of things is really wrong for the post filters, because for me it is more useful to use them on the delayed signal only, otherwise I would just use an EQ plug-in after to do the same thing. 
