The Meaning of Life, the Universe, and Everything.
I feel like it's time that in the next update you're finally able to connect minecarts to trains and there are more types of rails too - like for example in the mod "railcraft". When I posted this suggestion on reddit it got deleted, because you aren't allowed to post suggestions that are part of mods?! XD But turtles were once also just part of mo's creation mod, so I see no reason why they shouldn't finally implement things found in buildcraft or railcraft like autocrafting, rails and connecting minecarts.
This is honestly a fantastic idea with a high power furnace cart as an engulfing could make a very efficient way off clearing out many good sized cave systems and mining operations. Though I believe that a new furnace cart would be needed, one with a higher output to pull more carts; perhaps a new consumable that fives more power. Or maybe a new cart altogether.
Though the addition of powered rails makes this either a complex idea or an obsolete idea.