The only problem with using ender pearls as an example would be that it is actually really easy to set up an ender man experience farm. Along with this free experience comes free ender pearls. This farm can be made in standard minecraft, but redpower simplifies it further, requiring only normal pistons instead of sticky pistons. Unfortunately, other mob drops are nowhere near as rare. It is a good idea, but would probably need a whole swarm of keywords. Then, players would need to go through the complex path of transmuting things to remove as much keyword cost as they can. On top of this, keywords would need to be very well balanced and thought out, so as to retain standard EMC (or its new equivalent) ratios, like 256 cobble = 1 iron, 8 iron = 1 gold, 4 gold = 1 diamond, 1 diamond = 8192 cobble.
Above is pure ideas, and may not make sense, use as you will.