Any suggestions?

If you want Fun build, so play it. It's for fun so you can fly anything you like. If you want tips on competitive side, that's a different matter

Fun it's good, competitive this list is not good.

Sheild upgrades are pretty expensive (although with regening astromechs I get where you are coming from). I would rather replace the shield upgrades with either Integrated Astromech (saving 8 points in total) or Autothrusters (saving 4). Both upgrades will significantly increase your survivability for fewer points than the shields.

Next I would consider dropping either Engine Upgrade or R7-T1 as they duplicate each other's effects. Also I don't think R7-T1 is the best atromech for Horton since he has a built-in reroll meaning Target locks are less valuable on him.

Personally I think you are spending a lot of points on upgrades that do not add a lot of value. If you want to run Horton and a pair of T-70s, try this instead.

30 Horton Salm, BTL A4 Y-wing, Ion Cannon

34 Poe Dameron, R5-P9, Integrated Astromech, Adaptability

36 Red Ace, R2-D2, Integrated Astromech, Comms Relay

Your T70s are now 2 of the best in the game. Poe is a hard-hitter who can tangle with most aces while Red Ace is the ultimate regerating tank. It keeps the same models and theme as your oringal list but I think it hits much harder.

Great advice! I improved my build greatly. I now have Keyan with VI and Ion cannon. I have Poe with R5-P9, adaptability, and integrated astromech. Finally I have Red Ace with R2-D2 and integrated astromech. I use Keyan to either slow the opponent down for the T-70s to regenerate or to allow the T-70s to attack from behind.

I just swapped VI for rage on Keyan

Just a thought, but depending on what you're flying against, the ion cannons can be a bit of a waste IMO. Many people are now flying either large ships or high agility ships so either you only hand one ion token to the large to no effect, or might whiff on the higher agi pilots. Either way, you need to run two ion cannons for them to really be effective.

Why not drop the ion for a tractor beam? Still offers an element of control for small base ships (and have them steer well clear of asteroids), and can really hurt the larger base by further reducing their agility and to set them up for poe and red ace (depending on who you're flying against, you can adaptability Poe down - remember, you only have to declare up or down when placing ships and have keyan shoot first and poe second).

Then, throw PTL on Keyan and take full advantage of their skill. Rage is a semi-waste as you still get a focus token and that second token will limit actions/moves then next turn (you'll still have to green after spending one of your stress on eyeballs...). You now also open the opportunity to barrel roll and focus/TL to reposition.