Hmm, I know what you want to do. I think I tried something like this in FE7 myself. What I did was to set the condition of the Unit to 4 (Dead). Now I see that this is stupid because what is if the unit is actually dead, because I used the command to change unit groups for the next chapter. Well this were my first times with FE7 I guess
But I did this in FE8 myself and load a Unit on the Map even though it were not deployed with the UNCR command by adding it through patches. But after looking in the Event I figured out I didn’t use UNCR, but I am pretty sure I did have something like your Problem because I had a Problem where a Unit was on the Map but the unit phase ended before I moved the Unit because it didn’t count as a deployed Unit.
All in all, I think one of the things I ticked here or all could work by using UNCR could work but I am not sure. I don’t know if you tried these I ticked.
I’m going to preface this by saying that I don’t hack in FE7. However, my hacks have a lot of party switching, and so I think the flag you want set on the removed units is the escaped flag, which is UNCM 10000. In FE8, removing characters from the party is done with the REMU command, which sets the escape flag, so in theory, that would work in FE7.
l had figured this out last year. The answer is basically UNCM and UNCR as expected, but you gotta set or unset Escape+Tequila’s Capture (0x4010000). Setting Escape hides the unit from prep screen, but it also sets Tequila’s Capture, which also sets Escaped…meaning you can’t bring a unit back unless you unset both. l go into detail about it in the following post, but that’s the gist of it: How to bar a unit from a chapter? - #14 by Kemui52