Like others have said, it doesn't make much sense to do what you're asking about.
If you should decide to go ahead with this anyway, here's a maybe SLIGHTLY more convenient (and less expensive) solution:
The long discontinued Ampeg V4BH is supposed to have the exact same preamp as the SVT-CL (but obviously a different output section). At least that's what Ampeg's marketing said at the time. The V4BH was said to be an SVT-CL preamp with a 100w 6L6GC-based output section. It's the weakest 100w amp I've ever played. I own 50w amps that outperform it volume-wise, by quite some distance. In fact, I thought something was wrong with mine, so I brought it to an amp tech. He said it there was nothing wrong with it, but that these amp measured close to 50w and were "electronically weak", whatever he meant by that. The TONE was nice though, and the power of the output section won't matter for your needs. You can probably find one considerably cheaper than an SVT. It is also a LOT lighter than an SVT. I don't have the exact numbers, but I would guess around half the weight.
Just to be clear: I'm talking about the V4BH that has the same visual appearance as the SVT-CL. There were two versions, one with a blue script logo and one with white block letters. I have the one with white block letters, but I think they are both the same internally. It's a nice little amp for recording, but utterly useless with a loud band. It was simply too weak for my volume needs at the time (and it didn't exactly help that I matched it with Ampeg's recommended cab for this model, the extremely inefficient, boomy/muddy sounding SVT-410HLF, which is by far the worst sounding bass cab I've ever owned).
I'm NOT referring to current or vintage V-4B/V4b/V4. These are totally different amps.
I don't recommend going this route at all, but if you do, a V4BH will be probably be much cheaper and definitely much lighter than an SVT. Apart from that the disadvantges will be the same as with an SVT head, like others have already explained.
