I really like your MLP45E rules, and have been using them for a campaign I've been running (admittedly with a few tweaks of my own), really looking forwards to what you do next.
Got a couple of questions though. The feats Everfree Elixir and Essence of the Everfree seem redundant with each other (Page 50), and I can't find the table of hot air balloon prices mentioned on page 82.
Oops, good catch. Everfree Elixir is the early draft of Essence of the Everfree. You can ignore it.
The balloon table didn't make it to the final version yet, and I forgot to remove the reference to it. If you have the D&D Player's Handbook, I would put them at double the price of an equivalent seafaring ship, for the time being.