An interesting take on things.
I'm fairly close to your thinking, with a few exceptions.
I started collecting in 74, and more seriously late 77 when we moved to a town with a card shop. And one right on my way home from school too! Best part was they didn't mind if I hung out there.
Collected pretty much 74-84, was a lot less active till 88, and have been active/less active off and on since about 96/97
I felt the same way about grading at first. Pretty silly. I mean, really dropping a few grades because of centering? It should be about how well preserved the card is not how well made it was.
So I didn't buy any graded cards till 2000. My first one came in a pack......Guess the product?
I came around a few years ago, some stuff I still don't like, but I started seeing some really big price differences for graded compared to ungraded especially if the card was really nice.
I've sent in a few prewar cards, the better ones in the collection. Mostly because of helping a friend sell of a relatives collection. Sorting mostly, but they didn't really know much other than he'd spent a bundle so the pile of stuff must be worth something. I figured that even though my wife knows a decent amount about cards, selling the better stuff would be easier in a slab if something bad happened.
So I sent a few in to SGC. Mixed results, but they showed me what I'd missed a couple years later and while the cards that I was disappointed by look great, they do have some small issues that make them mid grade instead of lower high grade. Like 4s instead of 6 or 7s.
Other than some cards that are "better" even in low grade I haven't bothered with the bulk of the collection which is often p-f through vg. Pretty much anyone can grade those
Having handled loads of old cards back when dealers usually kept them in loose stacks, I'm less worried about altered cards. Especially if I'm at a show and can get a good look at it.
I've picked up a few that have done pretty well online, usually for about the VG price or less. People just won't usually go big on prewar mid grade that's not graded. (Think like $40 for a T206 that graded as an 80)
I eventually sent in a handful of modern cards. Didn't do as well as I'd done with the prewar stuff. But I'd paid nothing for it and sent it on a special so it was a cheap experiment.
I know it's done a lot, but cracking a nice 4 to sell it for more doesn't sound all that swell to me. Frankly, I've had better luck being very open about an items flaws and using really good scans.
Overall, I'd say send in a few. It's kinda fun. For me it was neat to see the cards I thought were really nice get a semi official stamp of approval. And while I can't ever hope to compete in the registry, I entered them and found I was pretty happy with where I was. And a bit let down later when I added the rare cards that were only As and 10s and brought the average under 50. Not really sure just why I cared, but I did.
Sending in a few also made me better at seeing the grades. So hopefully I can eventually send in some more modern stuff and do well. Of course, I'm usually spending the money on more cards or stamps or a new tool or.......
Steve B