Its a good idea. Whether it will work or not depends on why the old one failed. Drainfields fail for alot of reasons: plugged by fat, grease, or, sludge blown out of tank due to lack of pumping, overgrowth of biomass reducing permeability, roots, high water table (maybe seasonally high), compaction, soil was never really that permeable to begin with (clay). The only two or three that may allow you to bring an old back one online are biomass overgrowth, poor soil permeability, seasonal high water table. The best way to go would be to alternate between both drainfields with a pump and timer. Field 1 would get first dose say at 7am, field 2 next dose at 8am then back and forth all day. If there is long periods say more than a day or two between doses the microbes will starve to death. They will regrow but it takes a couple of weeks to a month. No microbes no treatment of the waste water. The drainfield is not just about disposal its where the majority of the treatment takes place.
Sorry for the long answer