Oil primer over latex

Here's the deal: I replaced the planks on my deck last year with new pine and painted it with "self-priming" interior/exterior porch and floor latex paint. Of course you know what happened--as the snow came off the deck, so did a lot of the paint. Yes, I know what I should have *done*, but the question now is what should I *do*. Is it reasonable to scape off the loose stuff and put an oil-based primer over the remaining latex before repainting, or am I doomed to stripping/sanding off all the "old" stuff before priming? I don't plan on being in this house long enough to enjoy a super-quality, last-forever paint job (hence, my minimalist approach last year) but I do need something that will last at least a couple years.
Thanks in advance for your opinions.
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