I recall a smarter way to handle differently scaled opponents (say, a Tie-fighter and a Corellian Corvette). Instead of rolling more dices, the results were capped to a maximum (in this case too you'd have an advantage on damage/resistance rolls on the bigger one, and on dodging on the smaller one).

That's the second edition rules, before Revised & Expanded.
Now without looking those up, so I may be wrong. But the scales worked by capping all the dice in certain scales, similar to the extra dice.

So everything compared to Character Scale, and the differences calculate out.
So Speeder Scale the dice are capped at 5's, so all 5's and 6's are just counted as 5's, for Character damage done to a speeder, and for Speeders trying to hit characters. With a similar effect to the extra dice, of making it harder for a Speeder to hit a character, and harder for a character to damage a speeder.
Obviously the die caps work the other way, so a speeder dodging, and a character taking damage, both being capped at 5's.

The other scales I seem to remember being,
Walkers Scale had a cap of 4.
Starfighter Scale had a cap of 3.
Capital Scale had a cap of 2.
And Death Star Scale had a cap of 1.

But it's been a long time since I played 2nd Edition, so I may have forgotten the exact details.

I would have to look it up myself, but I remember my interpretation that any rolls above the die cap didn't count at all. In other words, if your die cap was 4, any 5 or 6's rolled counted as 0. The tables, also if I remember correctly, were not labeled well and the reader had to use some fancy logic to interpret which direction the die caps worked on which roll (i.e. the starfighter's die cap when dodging the character shooting at it versus the character's die cap when rolling to damage the starfighter).

I've moved on to my own system based on Open d6, so I haven't looked at either edition in a while.

The system as you describe seemed worse than I remember, but I wasn't sure, so looked it up, and found the following quote, "Tirog has a die cap of 4. When he rolls to hit, anything above that 4 counts as a 4.". So you just adjust down any dice to the cap.
On a quick scan of the rules I couldn't see what happened to your wild die, so if you rolled a 6, whether it's value would get adjusted down, but you could roll again and add that value, or whether you just can't roll a 6 on the scale system.

But you're 100% correct, the system isn't as simple as I outlined above, as you get different Die Caps depending on whether you're hitting, dodging or resisting damage. For example Speeders have a Die Cap of 4 to hit Characters, but Characters have a die cap of 3 to resist that damage.

I also noticed that Capital Ships get a die cap of 4 to dodge vs Death Star Scale (so are easier to hit by smaller and larger opponents), and Starfighters suffer no die caps to dodge any scale of attack, it's really weird & confusing and I can see why my group jumped on the 2nd Edition R+E rules when they came out.

Having a quick look at the Open D6 rules, the scale modifier system is quick and elegant, I like it. Do you use a standard amount for converting across each of the Star Wars scales (maybe based on the average roll of the old scale, so 6 for a speeder, 12 for a walker)? Or come up with values on the fly?

I stand corrected.

I altered the whole thing to what I am calling a tiered success system. My group decided the whole rolling dice for hull or the character to resist damage was a little too random, so hull, strength, and armor became static numbers for damage resistance.

Unless otherwise noted, such as damage resistance, rolls are compared to a base 10 (0 tiers of success, or 0T). Dice are added from lowest value to highest (any pips are included first), and any remaining dice are tiered successes (so a 4D roll of 3, 3, 4, and 5 is 1 tiered success or 1T against a 0T target of 10). Range, cover, etc. increase the required tiered successes instead of the target number - much quicker to determine the "target number."

To dodge, the target must roll more tiered successes than the defender. Vehicles (which include walkers) must roll 1 tiered success more against characters to dodge (i.e. a character rolls a 1T success, after accounting for other modifiers, against a speeder; the speeder's pilot must roll a 3T success on his dodge - must roll more tiers of success, and is at a penalty of +1T for scale - to completely avoid the attack). Conversely, the character's damage roll must result in +1T to even get the "ionized" result on the vehicle. Except for the transition from vehicle to starfighter scale, each level of scale requires an additional +1T, applied to the party it would penalize (i.e. a vehicle must roll +1T above a character's dodge, after other modifiers to hit). Damage from larger to smaller scale is slightly more complicated.