Hi Grobyc!
I tested a Little with the ps1 and radical dreamers version, I can't put elements on Dark Serge's grid yet but now I know how the grids work:
First, there's the bit flags, they add with the elements slots, for example: beach bum has for elements on level one so, it's E0 and the four first slots are represented by two bytes: the first, the element number, for example, miguel's holy dragon sword is 1DE so, ir would be, in little endian, DE the frist byte, and 41 the second. Enemy techs tend to use 41 but some use c0, just like ally techs, I'm not sure but I think you can change holy drag sword to level 3 in the menu and set it as " c1" so it will definitely be unremovable.
Next, you can now manipulate character grids! For example, Guile: On the ps1 version, go to harles battle data section on file 2524, just do 16 * B0 in the calculator, and then, look at her grid growth byte, it's 7. now, head to guile (2*B0) and change the growth bite to 7, now from byte 30 starting from byte one, select 70 bytes and it will cover his grid and bit flags, you must pass harle's to his, that will make his grid as large as hers. That's all i've' discovered so far, ah and I'm playing with the stronger versions of doppelgangable monsters now to, for example, if you turn into the stronger version of wingapede, he'll keep he's elements but be stronger.