People who invested in Apple are different because that money is being used to help produce jobs, goods, and services. Those who buy BTC are not "investing" in the creation of the Bitcoin software, they are merely investing in the Bitcoin blockchain which has no useful intrinsic value of its own, it is merely an aggregation of data that is just tallying where all the money is moving.
Hmm. What if your investment in BTC raises the price enough to attract commerce. Is that not indirectly providing jobs?
Your proposal misses a big sore point. If it passes, then the value of *your* bitcoins will seriously diminish. The guy who mined already got his profit, so the loser would be *you*, and all the other people who are buying old coins now. You might not worry so much, but I expect that just about anybody who has invested in bitcoins will not cooperate with your proposal, i.e. everyone on this forum. Therefore, you'd be much better off taking your proposal elsewhere and begin a whole different project, based on bitcoin, with just the btc convertability you suggest, but appealing to a whole new audience, not to those who have already invested in btc.
Another point, what about bitcoin mixers? If I send 100 bitcoins to a mixer, then eventually I get 100 bitcoins back, but they could be newer, older, or a mix of newer and older coins. There'd be no way to tell who got what. The 'penalty' to early adopters would be completely random.
In the long run, I'd say you'd be simply better off starting a new block-chain, in which old bitcoinsPlus, in every transaction, are converted to new bitcoinsPlus, in proportion to the difficulty now and the difficulty when generated. Of course, then there'd be no incentive to mine now, since you get the same reward if you mine tomorrow, or next year, so I'm not entirely certain that it would take off. Perhaps it would be more popular amongst socialist idealists.
As for the crux of the problem, perhaps we can hope that, eventually, older bitcoins will gradually enter the market as the early adopters spend/retire. Not unlike the gold rush of the 1800s I suppose - fortunes were made there too, and all they mined was a useless soft yellow metal.