The trick is to mimic the effects of the HDR and update with "new" technology.
1. Radionics tuning: actually brilliant when you think of the individuality of matching the device, the desired task, and the user's subconscious.
2. Synchronization of both hemispheres of the user's brain: the head coils and enhancement with use of audio similar to Hemisync audio of the Monroe Institute.
3. Synchronization with the "second brain", i.e. the gut: the electromagnet over the solar plexus/stomach chakra. Possibly something less powerful than a 300 volt big ass magnet, this needs more research.
4. Stimulation of the Pineal gland: again the head coils, but the audio could add to this and possible pulsed lazer stimulation of select acupuncture points of the head/ears, along with visual stimulation via LED mounted in googles.
5. More detailed instructions and exercises: videos and "guided audio" time travel adventures.
6. Keep it affordable and build-able: open source schematics. There will always be users who will purchase a unit from those who can build, free market will keep cost down and quality control.
Yea, I've been thinking about this for awhile.