And both needed a lot of time to develop...
You're correct, and it's a pair point to say the signing wouldn't be ideal. But, I think we need to look at the situation as objectively as possible.
It looks like we can't currently afford to sign a top quality, first choice right back, so to simplify the situation a bit I'd say it leaves us with three realistic options.
They are a) do nothing, b) sign a short-term stop gap on loan or c) buy a young prospect who may challenge for the first XI soon or even now.
Putting it that way, I think most would admit that C is the best option out of a far from perfect situation as long as we genuinely believe he's a good prospect.
In an ideal world, we wouldn't be relying on Seamus for the season but we're not in an ideal situation - far from it.