The only downside I see currently is the need to put the mine into the mercs primary hand. However, we can't simply use a similar item from sector inventory because item status matters, you know? What we could do (maybe) is to "load" another item of that type from the mercs inventory into the primary hand. With that method you could place one mine after the other. You'd only need to load a bunch of mines on the merc.

Small convenience feature - improved bomb planting.
With new option IMPROVED_BOMB_PLANTING = TRUE, if you hold SHIFT key while planting new mine, then another mine with same item id will be taken automatically from your merc's inventory. If no such item found, any mine will be taken. If you plant tripwire-triggered mine, then only tripwire-triggered items will be taken. This new feature work only in realtime.
If you are making tripwire network, then this feature can be used to plant another tripwire item with network and hierarchy settings taken from previously planted tripwire. You just plant tripwire as usual, selecting it's settings from dialogue, then if you plant another one while holding SHIFT key, those settings will be used for new tripwire, instead of showing you dialogue.