Magnatize everything. Then if you don't like something change it. I would take the emp over the base oberon, you shouldn't have to mod anything on your current bb hull to make this but once again magnatize! this way you can make both

. Apoc is meh with the base rules, you'll probably only field the emp :/.
Tyrant/ Armageddon combo is powerful midrange for Imps 16fp and 4 lances on a broad side @45 (counting the geddons dorsal) is nice.
If your going to take a mars you almost have to take a dominator (or something with a nova cannon as one nova tends to... blow, pun intended

) I tend to prefer the dictator for smaller games, 750 or less, and the dictator+ emp should be fine for games to about 2k.
Dominator/ gothic or lunar/ lunar is a mainstay but remember single novas are eh. Endevours are ok, if you have torp dauntless available play it as a stand in.
+1 to 3 groups of 3 falchions
So Emp+ ab 370
Geggons (2) 490
Tyrant+45cm 195
Dictator 220
Lunar (2) 360
Endeavour (2) 240
Falchion(3x3) 315
2190
If you take a sa (150) and 3 rr (150) you still have 510 for sm so 3x3 hunters and a strike cruiser.
Blast marker rules are stupid if you are smart enough to maneuver your ships into a position that they will not put bm in each others way you shouldn't be punished for it. That rule cam about from problems with (if the bm is at the rear of the ship does it have -5 cm speed still) or (do bombers attacking a ship with bm in base contact have to roll D6 and be removed on a roll of 6) etc...