Now when we have the Lambda - I started wondering if I could craft a house rules for the Upsilon and TIE/sf.

Looking at the specs, Upsilon should have intel for the sensor array and strategic for the shuttle aspect. I'm quite ok with just changing the Relay to Intel on Lambda...

But how to upgrade TIEs while keeping them cheap?

TIE s/f looks a bit like black squadron for me.

Same as a plain TIE, but with Hull 4 for the shields, Counter 1 for the turret.

Cost 10?

The TIE/SF is not the basic, cheap, generic TIE. That honor belongs to the TIE/FO. For the TIE/FO? Probably up the hull to 4, maybe trade a blue anti-fighter for a black and bump the price to 9 or 10 points. The main improvement from the earlier TIE/LN is the addition of combat shields.

TIE/FO would be the 4hull essentially a TIE squadron. TIE/SF would be 5 hull since it only resembles a TIE fighter, its not a TIE fighter in almost every other way. They are a lot heavier and have more stuff, including much better shields.

It also has a gunner turret so it would probably either have a 4die attack or have a "split fire" rule

Split Fire(2): After attacking a Squadron, you may perform another attack against another Squadron using a 2 blue die anti-squadron attack.

Probably would make it 14/15pts as its 5hull, 3 speed (theyre a lot slower than TIEs with the excess equipment and guns) 3 blue Anti-Squad attack 1black Anti-Ship attack and the Split Fire ability. One could argue they should have Rogue too since theyre primarily special mission ships often on their own or in pairs but that would probably pricehyke them too much.

I agree the UPS would probably just be a Lambda with Intel slapped on there, though probably instead of Strategic not Relay. Also +1 black die since that thing does have some good guns.

I honestly believe the TIE/SF would have counter.

Counter seems to be split between representing super amounts of speed and maneuverability (A-Wing, Interceptor) and absolutely no maneuverability, but turrets... (YT1300, HWK, VT-49)

The TIE/SF has all of the above.

So it'll probably have Counter.