I've looked into this as well.
The HDI rail spacing is very close to the ALH injector spacing- if that won't work I'm sure some custom short high-pressure lines from the rail to injector can be made.
Like DPM said, the CP3 pump has the same bolt pattern. You'd need a smaller pulley, as I think the CP3 needs to turn about 1:1 with engine rotation to provide sufficient pressure. The HDI pulley might work but then you'd need to shorten the timing belt.
Control: here comes the expensive part. As of right now, there are two standalone Common-rail management systems on the market that I know of- Bosch Motorsports has one, the cheapest variant is around $3500 the last time I looked. The other is an independent tuner in the UK, and I think the price was around $1800. Adapting a Cam sensor and other electrical bits is the easy part. Both systems come with high-voltage drivers to run the injectors as well. In my opinion, it's only a matter of time before a DIY solution shows up, if these standalone boxes end up in the hands of some clever coders, the routines and algorithms needed will start showing up and pretty soon people will start building their own.
I don't think any of this is out of the hands of semi-skilled individuals, but the cost involved, mainly with the ECU, is sorta prohibitive right now.
The main advantage I can see with Common-rail is much better and more controlled fueling at higher RPM's than the VE pump can realistically handle.
Brendan