Because of the IFS strut set-up on the R50, there are two "viable" options for those wanting to lift beyond the standard 2" coil set-up. I use the term "viable" loosely because either requires time and money, not to mention due diligence. These options are: SFD (affordable, practical and relatively easy) and SAS (can be expensive and more difficult but still pretty practical). I'd recommend the former if your mechanical skills are limited (like mine ) but some members have tackled the SAS option and have been successful.
Beyond these, you'll be hard-pressed to make anything else work. Coilovers would be an option but that would require some serious fabrication/engineering skills and a ton of money. There was a coilover thread floating around here a couple years back but I don't think anything come of it that could be useful as a real-world application. A European company called ProFlex designed the IFS suspension for the Dakar Rally R50 Terrano, which was extremely capable off-road but obviously very expensive (IIRC, I think each side ran around $2000USD at the time).
Based on what you're hoping to achieve, a SAS project would be ideal. It will allow for ample suspension travel up front and serious offroad capability. But if you're like me, the SFD option takes the cake because of its relative simplicity and cost.
In any event, best of luck!