You wrote so much words, yet you didn't describe how to diversify. IMO the optimal strategy is to actually keep everything in Bitcoin, because not only it's the leader of crypto market, it's also technologically the best coin. Diversification makes sense when there are close competitors, but there is no close competitor for Bitcoin. If Bitcoin fails, alts most likely will sink together with it.

If you like to invest in alts and most of your portfolio is alts, then indeed it would be stupid to got all in on one single altcoin, and it's better to choose coins from top 10 for the majority of your portfolio and from top 20 as a smaller part. But investing in alts is in general not as good as investing in Bitcoin. If you look at their prices, all alts tend to heavily lose in their BTC value, meaning BTC outperforms them.