I guess I'm not understanding the problem. I tend to consider an accumulation of plant litter as a good thing because it provides both structure and substrate for both the frogs and all the little critters you hope are growing in the viv. The litter accumulation also means you are locking up carbon, nitrogen, and other nutrients in a way that provides a slow release back into the system and thus avoids toxic spikes. Also, if the plant material is broken down too quickly by worms etc., you significantly increase nutrient turnover by breaking down the nutrients from large, to microscopic particles in one step. This tends to send the nutrients straight from the leaf, to the worm, to microbes like bacteria and fungi which are the true decomposers of the system. The microfauna like springtails, mites, and other goodies for the frogs tend to get bypassed in the process. The quick turnover of nutrients also encourages rapid plant growth which is not usually a good thing in a vivarium.
Of course I may be misunderstanding your particular conditions but in general, I'm not a huge fan of introducing things that rapidly break down dead plant biomass. I prefer that it break down slowly through multiple steps.
