I have two ideas that I think are pretty good.
#1. Add in a Chunk loader block that loads just the chunk it is on.
This block should look like a mini steve encased in glass and would have a config file to determin weather it could be placed by players/admins/op's.

#2. Some ideas for new and usefull turtle pereferils.

a. Crafting periferil! Craft a hoe with your turtle and it now has a hoe on one of its slots
This would allow it acess to a new crafting api that lets it interact with Workbenches & Furnaces. The hoe was chosen because it is the most constructive tool I could think of and it uses two diamonds, I figure that the ability to break blocks would be worth more.
b. Adv Storage Turtle! Craft a chest with your turtle and it now has acess to a larger invintory and more control over that invintory, it can also interacet with chests. If you have this on your bot then you should only be able to have 2 other things, most likely one of the crafting attachments and a wireless. the idea is that you have a max of the pereferils so that you cant make a super turtle.
C. Adv Crafting! Craft an empty potion glass with the bot and it will be able to interact with cauldrons enchanters and potion makers. the logic with this pricing is that by the time you have a potion stand you probably have plenty of diamonds anyway, and this makes the most sense

In conclusion!
The periferals should all be balanced, you should have a max of 3 per turtle, they should not be overly specialized, instead each one should provide nearly as many possibilites as the ability to create and remove blocks
Also maby have another one that can be toggled by admins that lets turtles act as chunk loaders.