If you are a new user, you won't be able to mine any block in any meaningful time, so your only choice is to connect to any of the mining pools, and this is already the case today, mining has been separated from the full nodes client since years ago.
Nonsense. Just because you don't have the money to do that, that does not mean that somebody else doesn't.
I did a calculation recently where I figured it would cost a minimum of six million dollars in order to carry out a viable solo mining operation. Do you seriously believe that someone who invests six million dollars into a mining operation would not be able to afford to run their own full node in a datacenter anywhere in the world? Even with two megabyte blocks the cost of running a full node is extremely low compared to the rest of such an operation, for everyone else there are the mining pools, the great egalitarian innovation that allows everyone to mine without having to run a full node and enabling everyone to be able to profit without excessive variance at a small scale.
Even if you are a new mining farm with enough R&D resources, you won't be able to construct 100MB block since there is usually only 1MB transaction every 10 minutes, maybe 5MB during peak. Unless you are an attacker intentionally construct huge blocks with lots of spamming transactions, you won't be able to construct a large block. But in that case the rest of the miners are rejecting such attacking blocks
In other words, having such a block size limit is stupid at best.
Agreed, which is why I think a hard block size limit is not even necessary, which is why my preferred implementation is Bitcoin Unlimited. Though many people are obviously still very uncomfortable with this idea so Bitcoin Classic certainly does represent a more conservative choice.