Without war caster...
Pact of the blade has an Eldritch invocation that allows your pact weapon (limited to one handed) to be your arcane focus...I can see a future DLC to include Hexblades (which can use any weapon as their pact weapon).
Staves (which are a focus) have been ruled to be usable in the same way as a quarterstaff.
Clerics can have been ruled to be able to inscribe their shields to make them work as a focus...that might be implemented.
What does a focus do?
Does it replace the somatic component of spells?
I found several focus items in the PHB, but at least in the part about spellcasting it is not mentioned what it does.
about 2h weapons:
You need one free hand to cast a somatic spell.
Can you hold a 2h weapon with one hand, like one end of the weapon rests on the ground, you hold it with one hand and the other hand is free.
You cannot cast and attack at the same time, but you could cast in one round and attack in the next round.
Prof. Dr. Dr. Mad S. Tist 
