As an potential engineering solution, the answer lies in two factors: the car and the track.
For the track:
With the increased downforce inherent in even the backmarker teams (I would wager that HRT and Virgin have decent enough aero packages to put several other formulas to shame, still), the challenging corners of our most favorite tracks are either conquered with verve (Monza, Spa), challenging due to other factors (Monaco, Singapore tightness), or removed because of outside factors (no more Turn 8 in Turkey). What should be done, then, to increase "risk" and the challenge of the sport is less of the Tilke turn complexes and more dynamic track shape. Someone else suggested more sweeping turns, and I agree. With more tracks that offer a variety of mixes between straights, chicanes, hairpins, and sweeping turns (rather than the Tilke "two straights connected by a bunch of squigglies") will be better suited. However, the criticism of tracks will always be there. Some are too fast, some are too slow, some aren't technical enough, some are too technical as to prevent overtaking. The tracks, also, are - literally - set in stone and to change them is to cause great financial burden. So, for my part, I would recommend....
IMO, the notion of "increased risk" tends towards pushing the car to its limits on the track. Those limits are imposed by the grip which, we all know, is determined by the aerodynamics and the mechanical grip of suspension and tires. The only two options to which these limits can be pushed is to either increase speed to test the limits of aerodynamic grip, or decrease aero attributes to bring back more halcyon days of mechanical grip and track ballet (my favorite historical year to watch is the 1967 season). Since no team is really looking forward to reducing aero benefits - after investing millions of pounds/dollars/euros/dinari/pesos/rubles/pooka-shells in wind-tunnels and CFD, the only possible answer is allowing an increase in power and speed.
With more and more tracks with less DNF-causing runoff areas, the FIA should really consider pushing engines to have MORE power than today, but with more fuel efficiency - rather than parity. If this becomes the new philosophy, it will benefit nearly everyone.
FIA: They can boast more power than before while using "green technologies"
Teams: More power, less fuel, lighter cars, faster speeds
Fans: Faster speeds, more "risk", some appreciation for the "green" aspect
Bernie: Faster cars, more interest, more relevance, more money for...him, I suppose.
Everyone: Better fuel-efficient engine technology
If F1 were really serious about reintroducing turbos, then the goal should have been to create more power than the current V8s (if not the old V10s). Bump it back up to 800 - 900+ hp and, with the same aero regulations, it becomes a matter of the team that can develop the best aero package (as before) combined with drivers with the stones to use all that power (as always).
(And get rid of the tire lottery, but that's a recent development).
In short: More power in cars = more speed with current aero regs = more "risk" on any track
**Edited for more power!**
**Edited for relevance to production cars**