I partially agree. Let's see:
First a reason not to keep it: spellmaking is a system which can be exploited big time. So perhaps some limitations could be necessary...
Second, "tweaking pre existing spells" as you very well put it may not be the only use of spellmaking. However, it was an important dimension that proved to be very useful and very necessary. Now, if spells scale with player's skill, this advantage of spellmaking will be made redundant.
Third, and here is where I partially agree with you: creating new spells out of existing spell effects added deep, RP possibilities and the like. Again though, this can be included to some extent if on-the-fly spell combinations are finally in. Of course you will be limited to combinations of just two spell effectsbut hey, I find this positive rather than negative. Being able to combine only two spell effects sounds like this more limited and therefore more difficult to exploit spellmaking that I was referring to in the beginning of this post. You can argue that this is too restrictive and too limited. For me though, it's a good compromise.
Tiny Lampe.
Well, they didn't scale with us in Oblivion. That's why I don't take for granted that they will now. However it seems like a logical step to me since Bethesda is trying to get rid of anything they consider redundant -and 5 different versions of the same spell, being damage the only difference, seems pretty redundant to me. We'll see.