I'd say the Issedone is clearly the predecessor of the Vandal at a guess. The Vandal was produced at Tokasha and the time period matches when it was under Bear control, and they turned it from an interceptor into a super fast recon and harasser boat.
And yeah as for the lack of DHS, look at the issues the DCMS had fitting DHS to Mechs in the 3050's (Panther 10K anyone?) perhaps there's some reason why they couldn't do it, so could be some kinda reason why these fighters don't have them yet.