What would you change about the following?

Weiss

Royal Guard

Imperial Officer

Imperial Officer

Storm Trooper

Probe Droid

Probe Droid

Command deck can be found here: http://ia-armies.com/army/hFJYdplZ

Note that I only own the core set + wave 1 expansions. I prefer not to pick up another core set, but maybe I should? I know 'imperial spam' is popular, but it also seems boring.

I wasn't sure about the last 6 points. Two alternatives come to mind, but reduce the activation count by 1 to 6:

-> Sub a probe droid and officer for an Elite Officer (might be nice for a second attack from Weiss)

-> Sub 2 probe droids for another Storm Trooper

Any thoughts and advice are welcome. I'm fairly new to skirmish.

If you're playing a big shooter like Weiss or an AT-ST then I think an Elite Officer is a great choice because it allows you an extra attack from that big attacker. But then you'll probably also want at least 1 Regular Officer to get the AT-ST into position to start with. So if you're working with Weiss then here's my personal suggestion:

16 Weiss

5 Elite Officer

2 Officer

...17 more points to work with

8 Royal Guards

...and 9pts left for Elite Stormtroopers (very strong with Weiss' Endless Reserves card) or for Regular Stormtroopers and a Regular Probe Droid (as you had).

One thing to take note of with the Royal Guards: their Protector ability only takes effect if the Guard is adjacent to the targeted space (not the targeted character). When guarding something like Vader or an E-Web, the Royal Guard can easily protect that character because it's easy to be adjacent to all of that character's spaces. But when guarding a large figure (AT-STs occupy 2x3 spaces), it's a whole lot easier for your opponent to target a square that the Royal Guard is not adjacent to, and therefore ignore the Protector bonus.

Because the Royal Guards are so difficult to use with a large piece, maybe it's worthwhile to skip them and take other figs instead. Here's a squad I'd like to try out:

16 Weiss

9 Elite Stormtroopers

6 Regular Stormtroopers

5 Elite Imperial Officer

2 Regular Imperial Officer

2 Regular Imperial Officer

40pts