Hi,

some of the eBay sellers of the 2.2kW spindles also offered a 3kW version with automatic toolchanger.
I haven't seen them for a while but I think the price was about $1500. Maybe they still offer them if you contact a seller.

Converting a spindle is very difficult - even with a well equipped toolshop and reliable plans. There are many parts that need to be hardened, precision ground and perfectly balanced if it should be more than just a proof of concept.

Christian