Good luck with a length like that. 28 length shorter than the shortened spear. 
I've tried using the bastard sword in secondary. It's not good by any means but still enough to handle a few unwary or inexperienced players without too much trouble. Thing you can't really do with a pike. By no means potential for primary weapon use but still suits role of the side arm well.
Just get some 1H or 2H prof if you want a backup weapon or use shortened spear, military fork or quarter staff.
Putting extras is WM is quite big demand just for a side arm. At least for me maybe 90% time spent on rounds is with the main weapon. On the polearms on the back, I cringe every time I see a piker/long spearist with a pole arm on his back. It just looks terrible. Surely efficient but I don't feel like breaking themed outfit with such things.
2h secondary mode like its now is way more logic.
Your suggestion is like... giving a pick a 2h option.
Sorry not following. Langes messer is a sword with 9 reach less than bastard sword that has polearm opt as secondary. Having 2h secondary for pick is a bit different thing don't you think?
