Steeping and mashing are two totally different proceedures.
A mash is used to convert unfermentables in to sugars that the yeast can then ferment out.
Malts that can be steeped, do not require the enzymatic conversion of the mash proceedure - the steeping proceedure simply 'rinses out' the fermentable sugars.
You could; as you say prepare 50 litres of wort from all pale malt, split this in to 2 or 3 batches and then add the different steeped speciality grains.
The resulting beers will all have their own flavour charachteristics.
Hope that is of use.