Company Acquisition value - approaches to maintain historical cost, historical accumulated and acqui

Considerations currently being evaluated are:

1) adding custom ledger types to hold NBV adjustments and Step-up adjustments

2) parent child asset relationships where parent equals FMV at time of acquisition and children represent historical, NBV adjustment and Stepup adjustment

Have you had to revalue your assets due to acquisition?  Did you maintian historical cost/accumulated and stepup by asset?  What approach did you take to do so?