I think we should take the 'convert cards to any time card' event. If we take the one that requires a mono deck for 4x upgrades, we can field at most 1 mono deck that we could -not- afford to lose with, and I doubt that we can even build a decent mono deck with our vault anyway. For the one that requires a time mark for 2x upgrades, the only deck I can see (besides the monotime) is a novabow with time mark, and using very few nontime cards.
If we take the conversion event, we can get a bunch of RTs, ghosts, etc, back. We'll still probably need to convert a lot of pillars/pends, but even grabbing 6-8 new ghosts/RTs could make a huge difference to us.