i believe you can
for example, the ultramarines suffered significant losses to their veteran chapter, so i believe that, seeing there strength now, you can use such a story line for your chapter
The First Company took heavy losses, not the chapter itself.
The Ultramarines are the chapter, the veterans were one company, roughly one-tenth of the whole.
There's a huge difference in company versus chapter.
Personally, I think that if a chapter were reduced to one single company of one hundred men, it'd be folded into another Chapter of similar gene-seed stock.
That's just my opinion, though.