Cardiff - Aberdeen and Malta slots
Routing via MAN / LPL / LBA to ABZ would seem logical, but then you are splitting loads.
this is not economical especially on an 18 seater like Highland. Also they are not likely to consider such a route without it being funded. If you look at their work, nearly all is paid for up front by Government work or contract work to large companies.
CWL - ABZ is probably only going to be worth 1 flight a day route to start. If you do MAN or LPL, you need a second daily option to get passengers on those sectors. This adds too much financial risk. At the end of the day all us airlines are about ensuring we stay alive and have the lowest financial risks for the next Winter especially.
re Malta slots, we noted that this company has slots at a number of airports for this Summer but most were given back. I suspect you are only seeing a slot position on CWL - MLA and not what is going to operate in September.