Buff it but make it slow like the Churchill I'd say. It's an infantry tank so that's probably more historically accurate and a 'light' vehicle that's durable rather than fast isn't something the game has right now.
Yeah I suppose totally revamping it's combat purpose would work, I quite like that, a sort of Heavy T-70 I guess? But yeah, you'd need it early, either 3 CP max or just allow it to be built from the platoon command post, in order for it to be effective. Just keep the recon ability at 8CP instead. The unit actually being useful early game would allow you to get some vet on it as well for once!
As I said previously, the valentine has a smoke mortar on it already. Allowing UKF to get it out early to deploy smoke for their infantry would give them a much needed offensive buff at the start of the game too, especially against MGs, without needing a mortar pit.
Would be a great "screw you" to a Panzer II rush as well. XD