ISU has been linked to 2 currently Keon Ellis (6'4 CG Southwestern) Justice Hill (6'0 PG Salt Lake CC) who have other P6 attention.
I would caution expecting any JuCo player to come in and start day 1 at an all Big 12 level the jump in competition is just as if not more difficult than for a mid-major transfer. I would expect Javan to be more ready practicing in the system for a year than anyone ISU could get right away.
As for the offense vs defense discussion, I think we can trust the staff to put a good offense system in, I believe they were 3rd in B12 scoring coming into last week. Even when this team doesn't score they are getting good looks (just bricking them). Imagine what a Matt, Naz, or Tyrus could do getting the looks that Prentiss, Tre, or Lewis get in the flow of the game.
Defense is the issue, small in the back court and slow in the front court is difficult to overcome with any strategy. Hopefully the infusion of players coming in will help that next year (Long Wings - Johnson, Dubar, Blackwell, Walker, Conditt develops and Foster skills).