LinuxGuru

If I'm understanding your question right, you'll want to call dologin.php?goto=clientarea in your form.

I've used ModernBill for years, tried AccountLab Plus, WHMAP and personally I feel that WHMCS is the best solution available. Although it's not perfect, and I hope for quite a few added features, it's very easy to modify and integrate into your site. AccountLab Plus is easy to integrate, but IMHO lacks compared to WHMCS. Different strokes for different folks. I'll stick with WHMCS. I do agree with some of the things you mentioned though.