There's just no way to replace the subtle differences with melanoidin and other compounds produced in a decoction mash. Step mashes, however, can be beneficial. Keep in mind, however, that mash temps should be decided by what characteristics you want in the beer, the malt analysis (or an educated guess), and your water. Mash step temps should not necessarily be followed by what a given recipe states. Many Belgian and German brewers specifically order malt to a certain degree of modification so that the beer can better benefit from stepped temperatures. Most of the malt available to homebrewers is very well modified, so one has to be careful, for instance, not to do a Protein Rest that would reduce head formation/retention in well-modified malts.