That would make ESG mines more like real mines and allow tactics like putting mines everywhere in front of entrances to your base and not worrying about renewal for some marks, while the enemy wouldn't know where mines are. Right now the invisibility of mines is useless, because one can see where an ESG unit is located and draw conclusions. A group of tigers driving through a semi-permanent minefield could be damaged considerably.
In siege scenarios, however, the ESG will be less useful, because putting mines in advance is not possible. More generally, the ESGs defensive use would be improved, whereas the offensive capabilities would remain rather unchanged.
The mines should not last too long, to prevent one player from putting mines on an entire map.