There is no such thing as a “changing the chain” in bitcoin. You are free to make no matter guidelines on your bitcoin fork you need, however bitcoin nodes are solely going to relay transactions or blocks which can be legitimate below the established guidelines.

As for the “exploit” you described, if we’re at top X, there’s a sure problem goal for block X+1. In the event you launch a batch 5 of blocks, you will nonetheless must observe this rule for every of your 5 blocks.

Additionally you possibly can’t “lease nodes”. Nodes are established as a volunteer system by people who like bitcoin, and even when you had been in a position to spin up 1,000,000 nodes your self, your fork shouldn’t be Bitcoin so transactions you despatched on it could not be relayed by Bitcoin nodes.

I might suggest studying extra about how bitcoin consensus works.