I think this is a great idea. I'm not sure if this is in it but if there are more ores in a vein when you vein mine it will take you longer and the less there are the shorter it will take. Maybe an equation should be
S×O/3, where S is the speed of breaking the ore without ore miner and O, is how many ores there are. So the speed of breaking the vein is still 3 times faster but not too fast.
Also, I think this should be transferred into an enchanted book so everyone can get it and they can put it on any tool they want such as axes, or hoes.
You may be sat there thinking how would this work on hoes. Well here is my idea you make your platform and use any block besides dirt to form you boundaries. This should work on level changes but if the community doesn't want it on level changes then maybe not.
With these suggestions it will still keep Vein Miner fast but not too fast, It will allow any rank to get Vein Miner on any tool but it requires Meebles, and it may work on other tools other than axes and pickaxes. I am not good at coding. I don't know if my suggestions are hard to implement or not. Please to not get mad for I have no knowledge of coding.