Well I totally misunderstood what you were asking in the first post then. The save/quit glitch is not something I have ever heard of but I just tested it out in terms to castles and it totally works. I don't know how you figured it out but it was awesome to test out. That should improve those longer missions for sure. Having 4 strong troops in one turn essentially should speed up the speedrun.

I believe these runs are Any% so glitches like this would be allowed. Maybe if the moderators see this post they can say yes or no to confirm.

I don't know if I'd call that a glitch but I don't see why that wouldn't be ok. I don't know if it would be a time save though at least in the Joan of Arc run. The last mission can save about 30 seconds if you get the relic in the top right corner of the map so I don't know if the save/quit method will save that much time. I say try it out though on other missions. Why not, that's the fun of speedrunning.

I had the thought to start mission 6 (Joan of Arc) first since its the most crucial with RNG and wait till you get the relic in the right spot but the rules for the run are: you start the first mission and end on the last one so that wouldn't work.