In my mind...short and simple answers...

High speed PIC's could handle the work...it's all about the guy behind the keyboard
High speed anything don't work too well in the automotive environment...it's all about the guy designing the filters.
9600 baud...not so much...as stated before. You want data transmitted every .4ms . Not going to happen at 9600 baud, I don't care how you program it, unless you want to start dropping bits and sending 3 bits instead of 8. Must go with much higher speed as stated earlier.
You don't want to learn or write in assembly? Well, that's probably not going to happen either. PBP's built-in 'ON INTERRUPT' is designed in such a way that latency is practically unavoidable in a lot of situations. Using DT's Fast Interrupts isn't that hard, and yes, it does require you to learn a little bit about ASM, not much though.

In my mind, any serious ignition work is best suited for a different processor, maybe a dsPIC...not that a PIC couldn't handle it...with the right programmer behind the keyboard. Personally, I think you're playing with matches in a gas fume filled room. One ignition event just a bit early, there goes the intake manifold, a whole load of events a bit early, now you've got 8 pistons that could double as doughnuts and con-rods that could do double duty as horseshoes.