Allow players to take level N assignments as level N-1 assignments requiring collateral.

This would be realistic - level is supposed to be confidentiality, the degree you are trusted by the NPC corp. You can be trusted for your past behavior, or you can be trusted because you have risked the collateral.

This makes it easier for more experienced characters to level their alts in a different location, which enhances the replayability of the game. It gives more options to newbie players - either do level one assignments, or somehow obtain the collateral and go and do the level two assignments. It makes alpha outposts more interesting to very new players, who may well be disappointed by their apparent emptiness.

One problem is that sometimes just being able to view the assignments gives out information about mineral locations.  In order to address this visibility problem, it might be possible to have a relation-purchase-sell mechanism; you purchase a certificate or license object that gives +1.0 relation with a given corp with your collateral, then go and do assignments one level above your previous level, then later (if you didn't fail or abort any of those assignments, which would destroy your certificate / license) you can sell your certificate or license back to the corp. A small gap between relation sell price and relation buy price would discourage "tourism".

Still, though comprehensive list of these assignment locations have not yet been leaked (so far as I know) into public knowledge, but it will probably eventually leak, and at that point, hiding the list will be futile.