Drag and drop while working is dangerous. You always drop something by mistake then discover it days after. Imagine scenario: you just created some complex material, applied it to mesh and put in central spot of map for that omph effect, then few min later you dropped some brick texture by mistake on that mesh thus erasing cool material. After rebuild editor purged it. Look for autosave and pray its there.
I guess you never heard of archiving-systems (like GNU RCS and Subversion ?)
Those will take care of any 'mistakes' like that.
And I'm not sure if the current UnrealEd is missing the feature that showed exactly what textures were used in a given level. That should make fixing mistakes like that real easy.
Besides ... planning > doing, it's something most people need to learn the hard way.
Do you really want to search through thousands of textures and manually enter their names ? (and pray to <insert favourite deity> that you didn't use nearly duplicate names in your list)
Also I have strange impression that UT always gets most bare version of engine possible. I remember watching tech demo movies after they released ut2004. Some of those things we just got for ut3 with titan pack upgrade, but many are not present. I only wish they turned UT3 into real tech demo and pumped better effects with each major patch.
It's quite obvious you don't realise the implications of patching software on that level. Even Microsoft rarely if ever adds any new technology to a released OS. So why would an engine-developer like Epic do the same to a released game ?
Besides ... if we get this kind of stuff 'for free' then they would kill their entire engine licensing business (why pay a few hundred thousand euro for a license if you can get the same stuff in a 60$ game ?).