This is a very good point! I'll think about it.
And I just came up with something. Railway mobile miner. It's a special wagon that mines ore in width range while on station (or special kind of station).
Player needs to pave the railway and electric line through multiple ore patches, and train with multiple miners will drain them sequentially.
I didn't figure out how to deliver ore from miner to production (miner itself shouldn't do that), and what additional infrastructure such miner might require. It's just a concept yet.