Unfortunately it is a choice between raster resolution and motion resolution as there is no 1080p/59.94 project.
If you select 1080i, then every progressive frame becomes a field reducing vertical horizontal resolution by half and basically edit on every “frame”.
If you select 720p/59.94 you will get all 59.94 progressive frames and be able to edit on each one, but will have lost overall raster resolution.
Hopefully “50p” and “60p” editing will come in a future release (sooner rather than later) as these formats are quite common now.
If output is for web and mobile, I would try to keep it progressive all the way – if for broadcast – then interlace project is probably OK but more and more screens are progressive.
Michael