Popps, to your OP - I think the way you started your post (and title) makes it sound like whining to alot of people. Even though I think your later suggestion on treasure chests is pretty good.
Is inscription or non-scrapper crafted books useless?
Not at all. Scribing scrolls is a great way to earn gold aside from hunting mobs. Plus it's much easier to churn out non-scrapper super slayers until you can get the scrapper versions (which is really really hard).
Even then, remember that the ultimate spellbooks - the scrappers - require inscription to make. The skill itself and a scribe's career is far from useless.
Besides, my crafter uses the LRC, MR, +Magery non-scrapper/non-event books. LRC spellbooks are really nice, esp since they are a blessed form or LRC. But by themselves, unless you get a great combo of 3 properties, don't sell well enough. I just fill them up and sell them as full spellbooks.
Super slayer scrappers are very highly coveted. But if you have ever churned out normal spellsbooks before, you know how rare it is to get a super slayer. I have made around 20 scrappers and have yet get even 1 super slayer scrapper to replace even 1 of my 6 super slayer books. (Though my undead slayer is the Conjuror's Grimore from the graveyard event. I don't need the +15 magery on an undead slayer though, but +15 SDI is definitely a good bonus...beats normal books. An undead slayer scrapper would be wayyy nicer.)
Meaning non-scrapper superslayers sell (very well) for a couple of mil while Scrapper versions sell for many times that. *Provided* you can even find 1 for sale.
Spellbooks from the town invasion generals
I have several perfect books with 30 SDI that dropped from generals during the town invasion part of the event. However, I rarely get the chance to use them and in fact have given up on using them totally (I play with legacy more and is limited to 4 alternate weapon config from UOA). Those books have a fixed number of properties that do not include the slayer property. In general, if I am using a non-slayer, I find that even Scrappers without extra properties are more useful if I want something with awesome SDI (Scrappers have only 5% less SDI - ie 25% SDI). If I need a slayer, I use the non-scrapper versions that I have.
The conjurer's is pretty nice though, undead slayer with +15 SDI. But I don't really need the +15 magery for a character that intends to hunt undead though. A scrapper version would be even better!
That being said, I think no one would disagree that if the devs intended to run events that gives special items for a limited time, it should be a limited-time only thingy. Or at most, run a similar event later, like TOT1 and TOT2.
Scrappers
So that brings us to Scrappers. If the 2 paragraphs above doesn't show it well enough, I think Scrappers are really really awesome. The only reason why normal crafted books are still useful is because Scrappers are really hard to make. So any changes that makes them easier to make will do precisely what you say in the post title - making normal crafted books obsolete.
That being said, it's really difficult to farm enough peerless regs to make enough scrappers and get even 1 superslayer...
So rather than allowing imbuing or selecting of mods on scrappers, I like the getting-peerless-regs-from-treasure-chests idea much more. Fishing not so much, unless you are talking about fishing up SOS chests and not regular fishing. But SOS chests should have less regs, just like SOS chests are capped at lvl 3. Say number of peerless regs = (chest level -2). Level 6 chests would in this case, have 4 peerless regs.
Other thoughts
As someone pointed out, it would be nice to have "Exceptionally" crafted items be actually better. Say, maybe have a minimum number of properties. As it is right now, things like tinkered magic jewels and spellbooks/runebooks have 2 separate and unrelated checks for being exceptional and the magic properties/runebook charges.
Also, I would love to be able to dye spellbooks, or have the switch weapon macro replace the item in my backpack at the exact same co-ordinates when I switch. Right now, they are just randomly placed back into my backpack and turns my nicely arranged spellbooks into a rather messy array...