Just a point… If you are in hi sec and a ganking squad comes along, your MTU will not save you. Corcord response times are:
0.5: Roughly 19 seconds
0.6: Roughly 14 seconds
0.7 : Roughly 10 seconds
0.8 : Roughly 7 seconds
0.9 and 1.0: Roughly 6 seconds
What this means is that between the first shot and when concord arrives, this much time passes. Gankers want to kill you before concord arrives and jams their ship.
If it takes a minute to anchor and online an MTU, you will be dead before you can switch mods.
Also, if you have a weapons timer… Such as one caused by having your drones aggress another player, you cannot refit until the timer expires. This is 60 seconds. So refit then engage or you may not be able to refit.