I agree with you on many of the points, Razmo.
The idea of having some kind of user loadable sample playback with pre/post filter choice/mix in a voice architecture would be very cool. Same with percussion features like fast envelope times, envelope shaping and attack/decay mode. However I would rather like this to be part of a general voice architecture like seen on Tempest that can be use for multiple purposes. That studio multi-tool.
My guess is that the component price and board size of the Pro 2 filters are way higher than a Mopho module so doubt such a module would be affordable. Also I like the idea of extension modules but doubt it will be cheaper than the current module and polychain concept in DSI modules.
So how about a desktop module with percussion and sample features? 
Having it in form of a multi-timbral module without any keys on allows for more compact size and free choice of controller to use such expressive workhorses like QuNeo or QuNexus. Such controllers allows for more degrees of freedom than the standard row of black and white on/off switches.
I must say that I like your idea of analog/hybrid percussion synthesizers operated from a pad controller. My guess is that you will soon regret that you sold your Pulse 2 and possibly MBase11/MBrane11!
I agree that some of the idears I have may be either too circumstancial, or expensive, but it will have to be specificaly tailoreed for percussion synthesis, otherwise you could just use a normal synth like Evolver or even Mopho for this, but those are not optimal in my opinion.
The main idear was to have a single drumvoice in a single unit really... Personaly I'd be happy even with a device that had no physical controls at all, so that all control and editing would be via an editor, but I don't think that many others would want it that simple, so I'd let the interface be up to DSI.
I would not want to give up on the dual filters to be honest, and the flexible routing because that will be a crucial part of the sound design options.. Maybe I'd even say that I'd like something new there, like four individual filters that could be used at the same time... a LP, HP and BP, individualy routable to the oscillators... If you wanted to forget about routing the oscilltors into filters, I'd be happy with three SEM type multimode filters, one hardwired for each oscillator... the point is, that I see the three oscillators as three distinct sound parts of a single drumsound, and each would need to be sculpted differently... I'd also like the engine to have dedicated envelopes for each oscillator's/filters parameters... throw in an analog distortion at the end... maybe even one for each oscillator, and finish it off with the P6 FX section, but with new FX tailored for percussion sound, and make it possible to control the routing of the FX as either serial or parallel, so that it can be used both as ambience (echo and reverb), but also insert FX (distortion, compressor, EQ etc.).
You could even diminish the engine, by only having one analog oscillator, and one multi-functional digital oscillator, that can work as both the ordinary Pro2 oscillator, but be switched into using samples... that may even be smarter... especialy if you decided to leave out the analog oscillator and made the front end 100% digital... in that case two such digital oscillators could give some nice options (but I know DSLSYNTH, that you'll be grinding your teeth at leaving the analog oscillator out

). In my opinion though, an analog oscillator may not really be needed, if the digital ones have been tailored for consistency etc... in fact I think I'll prefer that to any unstable analog oscillator.
The Character sectioncould also be expanded... I can see many fun digital mangling parameters being added on an oscillator basis, in addition to the mod matrix audio rate modulation.
More or less, it could be a synth as well... would not mind, as long as the engine is made for individual control of the oscillators... maybe the Pro2 architecture is even close to what I could use for this... maybe I'm just still dreaming of the Pro2 engine in a small desktop device...