No and yes.
No you can't disable the shields of a fighter/bomber.
Yes, you can use a sexp to drain the shields on Alpha 1. But they will recharge after a while.
Use this code to drain Alpha 1's shields:
when
--true {when you a ready}
--do-nothing
when {chained to previous event}
--and
----special-check
----6
----special-check
----9
--do-nothing
It may sound a bit wierd (having an if be a then), but it works. The special-check sexp is in the Training sub-menu.
Here is a list of the known special-check functions:
0 - no effect?
1 - no effect?
2 - no effect?
3 - flash front shield quad
4 - drain front shield quad
5 - recharge all shield quads
6 - drain left/front/rear shield quads
7 - no effect?
8 - no efect?
9 - drain left/right shield quads
10 - no effect?
11 - no effect?
12 - no effect?
13 - drain front shield quad
2000 - does something... but what?
Hope this helps.