This is a little note, but I think you want to be stating "intersystem" when referencing something that's travelling between systems. "Intra-" refers to something moving within - much like a standard fighter jump. Check me on this if necessary...
A destroyer or cruiser certainly has the power to move into or out of an orbit with little problem. Doing that requires quite a bit of power, and there's no shortage of that on any FS ship I know of. If modern space propulsion has the potential to get across the solar system at a reasonable pace (well, you won't see that soon because of governments and economies...

), the FS ships certainly can do it. And do it well.
However, that doesn't bode well in warfare, where speed in the operation is critical. Thus, unless it's a peace-time op or patrol, you're not going to see the good ole' GTD GenericOrion paloosing through the planets of the Vega system. Because of the ferocity with which FS ops take place, I have no doubts that the ships in question are highly mobile. They'd have to be or they wouldn't survive! Subspace travel thus augments that capacity by months and days time, depending on the size of the system and the power of the ship of course...
Long-term survival in space is critical for the FS-verse. We know there's systems with planets, but which are habitable? One would assume that during Reconstruction you'd have situations where you'd encountered people who'd never been "planetside" before. Loosing Capella would only augment the number of people like that. For Terrans and Vasudans in the FS-verse, living in space must be a norm, not just a temporary endeavor. As such, ships in the FS-verse are designed to last and last. Canon material would seem to suggest this. Thus, long-term space voyages would certainly be possible. However, they're not practical when you could just use that new node you just found...
So, I don't think travelling slow across a system would be impossible. But, it would in most cases be doable with FS ships.
...And, interesting side note, Proxima and Alpha Centauri are only about 0.205 LY from each other. Given the massive gravity well that would ideally be formed by their close interaction could make for a logical site for a node. One would also like to assume that the resources in the system would be of great interest...