as a hobbyist and modeller of pre-heresy marines i think GW (and FW) shouldnt.
one of the novelties of making a pre heresy army is that its YOUR army. noone else will have any models quite like it.
things like maximus aremour for marines I(like the FW red scorpions) and the older mk landraider (again made by FW, though its not really the pre-heresy pattern) are fine, but actually making full ranges of pre-heresy models is what im against.
many pre-heresy modellers (myself included) are proud of the fact theyve been able to make an army out of GS and lots of converting and that will just be lost if gw make full ranges of the stuff, with every noob who plays the card game getting an army of pre-heresy marines.
and these just arent my thoughts - many many people i know and many more who ive seen on forums hope that GW never make full kits for pre-heresy models.
for example: ive got 50 corvus veterans in my marine army, all made from actuall beaky models, either bought the hard way or traded with other people. im making a loyalist pre-heresy death guard army using the plastic maximusn parts from the BT upgrade box (i dont like the FW versions) and im up to 30. im proud of the fact that ive been able to get these parts and were they available normally, it would be no different to getting a box of marines. again, many people who make these armies make them becasue of the modelling options - they like the challenge of making a lot of stuff from scratch. i for one will not use my pre heresy models as muc has i do now if GW makes proper models for them (thered be no point: the models will no longer be 'cool' because anyone can make them, and the army lists suck, because all my armies are themed

but thats my problem lol)
rant over. sorry