Definitely a good idea to finish your ATPLs now before you get employed. I did it the hard way and wish I'd taken the advice I was given to knock them on the head ASAP!
I lean more onto the side of do the MECIR now. It would be unlikely you need it immediately, however, if you get a gig at a mob with twins you will be overlooked for the upgrade. Getting time off will also prove to be difficult, as many places run thin on pilots and to lose one for 6-8 weeks they are likely to be resistant. If you get some lucky timing the potential to progress quite quickly can happen. It doesn't happen to everyone, but if you have the full toolkit (ATPLs and MECIR), you are good to go on any opportunity presented to you.
And finally, although you shouldn't be doing it, and it will probably gets complaints, but having more IMC exposure will more than likely help you through a few learning experiences. I don't think the CPL course really cuts it concerning VFR flight into IMC (not IFR!) and a bit more exposure can help if it goes a little pear shaped.