How difficult would it be to convert model airplanes such as in this video, into attack drones to be used in Ukraine?

Probably all of the above.

These are really cool designs for the RC-F world. But some of the same things that make them desirable for hobby enthusiasts mean they’re hard to adapt for practical use in combat :

The small turbines provide speed, but have high fuel consumption that limits range.

The remote controls are programmable for custom flight routines, but they’re vulnerable to jamming.

Useful payload is likely less than 1500 gr.

They need about 100 meters of runway, and have no vertical takeoff or hovering ability.

There are probably some costly tweaks that could be done, but these things are meant to be fast & fun toys, not weapons. Kind of ironic since it’s a scaled down warplane.

There were 3 or 4 recreational RC designers here in OR that donated .45 scale models to Ukraine for testing & use early in the war, and their stuff never survived combat. Some nano designs like Black Hornet have succeded though.

Less war & more peace is the best plan for most human beings. But as always, I respect your destructive imagination Loli ♡

@JLoon hit on a lot of them. I’d also have to wonder about the strength of the wings and body when you add the weapons. Wings or pieces of the body could just snap off.

In addition to @JLoon‘s excellent list above, their outrageous heat signatures make them vulnerable to the cheapest Redeye, or similar, equipped man portable missles (MANPAD).
The cost balance is in the wrong direction. You want a $2k drone to take out a $13M tank.
Those models cost a fortune in labor.

That said, it might be worth sending one in somewhere so the enemy had to devote a vast amount of defensive resources everywhere in case there is another similar attack.

I’m thinking these are only useful in testing defenses against drones.

@Blackwater_Park – seems quite a lot faster than most 4 propeller drones.

“What man can contemplate, man can achieve.”

Great answers all above.

“seems quite a lot faster than most 4 propeller drones.”

Different missions. The slow and precise 4-prop drones dropping grenades down tank hatches are useful. The 4-prop artillery spotters are a gift.

A fast fighter-like drone would work better as a missile. Or for reconnaissance when air defenses are more threatening.