"By ’removing’ the jumper I’m referring to taking off the back panel and disconnecting the leads but then the tweeter wouldn’t function."
I think that may be a bit too far to take it on the LRS - plus - it might make it more difficult to sell them. I’d upgrade to the LRS+ first. And... I wouldn’t mess with the internal crossover. I’d use an external crossover as he suggests. Or, get the GR Research upgrade and build it as an external crossover and leave the internal crossover in place - just disconnect it / route around it. But... again... that may be a bit too far to take it with the LRS.
"The jumper is relatively easily to make, just a solid core piece of silver and bend it to shape."
That’s what I used (about 1/8" gauge) - works fine and inexpensive.
"It’s the fuse replacements he’s making (solid copper rod that he fills with something, not sure what material he’s using for that.)"
I just bought the copper tube (about 1/4" gauge) - works fine - don’t think the filler is necessary - shouldn’t make any difference.
"Do you know if the Class D website still sells the SDS-470C or if GAN amps are his new iteration? Ideally like to buy used (not so much for cost savings but because someone else burned the amp in for me lol)."
You could contact him to see if he would build one for you - but - I’d just opt for the newer GAN model - about the same price.
"I think the +s are probably worth the extra money (not sure how long you’ve had your pair) but I’ve heard they lose their amazing detail at first when they mellow out with burn-in."
I’ve had them about a 25 hrs of use - maybe - not fully burnt in. I hope they don’t mellow out - they’re superb as is! They sound a lot like the Quad ESL 57’s, at this point - which is "about as good as it gets!"