Yeah, I'm pretty sure that Tenshinhan could already fill the skill and strategy part. Like the guy in that video says, dude's got a shit-ton of moves, and he's been training his whole life, non-stop. He has the skill, experience, and the strength to actually do something. And yes, I'd much rather see Buu than Freeza. Hilarity would ensue as he'd turn someone into candy... and potentially try to eat them, only to have Vegeta slap Buu on the back of the head to spit it back out, or some shit.
Roshi, on the other hand... he took 5 guys down because the script said so, and that's it. Remember when he died by doing a Mafuba, back in DB? It seems that now he can do TWO Mafubas, a full-power Kamehameha, and still stand long enough to gobble a senzu bean. For a dude that stopped training decades ago, and can't even sense ki (then again, no one seems to be able to do that, now, for some reason)... that's a hell of an asspull power-up, right there.
As for Gotenks... again, he can vomit sentient chunks of C4. Imagine Piccolo tag-teaming with Gotenks, telling him telepatically what to do with those ghosts... instead of being Gohan's nanny. What a fucking waste.