The nice bit about having a Panzer 35(t) is that once you have one, you have all your bases covered. There was the single basic design. The Germans captured something like 218 of them, and while they were certainly used, they did not enter production, So there is not a parade of Ausf "X" models to deal with.
Whereas the Panzer 38(t) was produced to the tune of just over 1,400 of them, across 7 models (Ausf A to Ausf G). Not to mention several thousand being produced after the basic 38(t) stopped to be made into SP vehicles like the Marder III and Grille. And that doesn't count the thousands that were the basis for the Hetzers.
As for conversion possibilities, the "problem" is how much effort do you want to put into it. The A through D had small changes and adaptations between them. Where we enter trouble is with the Ausf E. It had 25mm armor plates added to the front and 15mm armor plates added to the sides. So if you are starting with an A thru D you can turn that into an E. But if you are starting with an E, removing those extra thick armor plates becomes an issue.
According to my own non-exhaustive list:
Ausf A = 100% riveted. Call this the base
Ausf B = Mostly riveted, a bit of welding. Small changes (Notek lights, gun sight cover modified, smoke grenade launchers)
Ausf C = Mostly riveted, some welding. Small changes (turret ring splash, German radio aerial, higher exhaust muffler)
Ausf D = Mostly riveted, some welding. Straight front plate, large stowage box on left middle fender
Ausf E = More welding, less riveting. Armor plates added. Changes include new driver and gunner visors, two smaller stowage boxes
Ausf F = Very similar to Ausf E
Ausf G = Nearly 100% welded. Very similar to E/F but both storage boxes have been eliminated.
So an Ausf A can become a B, C or D with minor tweaks. And an E can easily pass for an F or even a G with little effort. But crossing from those early versions to the later versions is the rough patch. I'm not sure what to make of the WG model, because it sure has a ton of riveting on it, and the E/F had more welding present, and the G had almost no riveting at all. So the WG really isn't a stand in for the final G version unless you snip/sand off all those rivets!